Ringworm is not a worm. Nor is it always ring-shaped. This misnomer of a term derived from an early inaccurate belief that the infection – which often causes a round, red, raised lesion on human skin – was caused by a worm. Unfortunately, this counterfactual name stuck and it continues to mislead to this day. 

Ringworm, or dermatophytosis as it is scientifically called, is actually a fungal infection of the superficial layers of the skin, hair, and/or nails. While a diagnosis of ringworm might give you the heebie-jeebies, it rarely causes serious problems and it is both treatable and, to an extent, preventable. Identifying ringworm infections at an early stage can prevent transmission and limit contamination, so dog owners should become familiar with the common signs.

RISK FACTORS

Although ringworm fungi are everywhere, there are conditions that predispose dogs to infection. Dogs that are at a higher risk of contracting the disease include puppies, senior dogs, and dogs with a compromised immune system. Other risk factors include poor nutrition, high-stress environments (such as shelters), high-density housing of animals, skin with pre-existing trauma, and living in close contact with affected dogs.

Certain dogs may have lifestyles that increase their risk of ringworm exposure, such as hunting and working dogs (including the German Short-Haired Pointer, Fox Terrier, Labrador Retriever, Beagle, Jack Russell Terrier, German Shepherd Dog), possibly due to increased contact with contaminated soil. Yorkshire Terriers seem to be more susceptible as well and are often overrepresented in ringworm research. 

The good news is that the occurrence of ringworm is relatively uncommon in healthy dogs. Even if a dog has been exposed, it does not mean that he will develop the disease.

CLINICAL PRESENTATION

Dermatophytes invade keratinized structures found on skin, hair, and nails. In dogs, the head, ears, tail, and front paws are the most common sites of infection, although they may occur on any part of the body. 

Ringworm infections tend to manifest as small, non-itchy asymmetrical patches of alopecia (hair loss), that spread outward on the skin. However, any combination of hair loss, papules, scales, crusts, redness, follicular plugging, hyperpigmentation, and changes in nail growth may be seen. The affected hair shafts are usually brittle and break near the skin surface, giving the lesion the appearance of having been shaved. 

In the early stage, the center of the lesion often contains light-colored skin scales, giving it a powdery appearance, and the edges are generally reddish in color. Vesicles and pustules may also be seen. In later stages, the lesion may be covered by a crust and the edges of the lesion become swollen. 

As these circular lesions enlarge, the central area may sometimes heal, leaving a circular lesion with central crusts or even hair regrowth. In some cases, there may be only one location of infection; in others, several patches may be present. As the fungus grows, the lesions may become irregularly shaped and spread, and individual lesions may merge to form large, irregular regional patches. 

Severe infections may generalize (spread over the body); as a result, the appearance can resemble demodectic mange. Generalized cases usually occur in dogs who are immunosuppressed, especially those that have adrenal disorders or have been treated with corticosteroids. Occasionally  ringworm infects a dog’s nails (as nails are comprised of keratin), causing them to become rough, brittle, and easily broken.

Fungi to Know

Fungi occur throughout the earth and have a critical role in most ecosystems. While the early fossil record for fungi is not extensive (their inherent structure does not lend to preservation), scientists recently reported a discovery in the Canadian arctic of a fossilized fungus estimated to have lived almost a billion years ago – which is even before the existence of plants! Suffice to say fungi have been around a really long time.

Early domestication of animals, such as cats and dogs, appears to have led to a later evolution of host-specific fungi. The group of fungi referred to as keratinophylic process keratin – a structural protein that forms hair, nails, feathers, horns, claws, hooves, calluses, and the outer layer of skin among vertebrates.  This group of fungi is quite large, but only three genera – Microsporum, Trichophyton, and Epidermophyton – are known to cause disease in animals and humans. 

The microscopic organisms responsible for ringworm infections belong to this keratinophylic group and are known as dermatophytes (derma = skin, phyton = plants). That’s why the infection caused by these agents is called dermatophytosis. 

Some species of dermatophytes are species-specific, meaning they infect only one species; others can be transmitted between different species of animals, including humans. The three most common fungal species that cause ringworm in dogs are Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes. Each of these are zoonotic (which means the infection is transmissible between animals and humans), but the rate of transmission is not known. M. canis is the etiologic agent of about 70% of the cases of canine ringworm; the remainder of the cases are from M. gypseum (20%) and T. mentagrophyte (10%).

INFECTION, TRANSMISSION, COMMUNICABILITY

Dogs who come into contact with the spores of the fungi may become infected if the dermatophytes infect growing hair or the keratin-rich outermost layer of the skin. Under most circumstances, dermatophytes live only in the dead cells of skin and hair and do not affect living cells or inflamed tissue. 

As a dog’s immunity to the disease develops, further spread of infection usually ceases, but this process may take several weeks and infectious spores can still be dispersed. Therefore it is a good idea to treat cases of ringworm so that spread of the contagion can be limited and the healing process and time is improved. 

While ringworm isn’t common in dogs, it is contagious and most cases of ringworm are spread by contact with infected animals or contaminated objects. Infected dogs shed spores into their environment, and spore-covered broken hairs are important sources for the spread of the disease. Thus, grooming tools, dog beds, toys, bowls, and home furnishings are prime objects for harboring the infectious spores. All of these should be disinfected if ringworm enters the picture. Ringworm spores are very hardy and can survive (i.e., be infective) in suitable environments for up to 12 to 20 months.

Ringworm fungi also resides in soil. Dogs who like to dig or roll around on the ground or stick their head in rodent holes may be exposed it regularly. While these favorite pastimes may expose them to the ringworm fungi, the likelihood of infection is not high; the establishment of infection depends on the fungal species and on the canine host factors. Susceptibility is increased when the dog has exposed skin surfaces (e.g., open wounds, cuts, scrapes, burns), as well as with high temperatures and humidity.

Note: Some dogs may be asymptomatic carriers; they carry dermatophytes on their body but do not develop any clinical signs of infection. These dogs are contagious and can contaminate the environment, which can be especially problematic in multi-animal environments.

A ringworm-infected dog is considered contagious and can transmit the disease to people or other pets including cats, pocket pets, cows, goats, pigs, and horses. Children (especially very young children), elderly people, and people with weakened immune systems or skin sensitivities may be more vulnerable to infection. 

Because ringworm can be transmitted to humans, you should take appropriate steps to minimize exposure to the fungus while the dog is being treated. It is important to wear appropriate protection (especially gloves) and wash hands thoroughly after handling an infected dog. Environmental decontamination and control are critical in treatment.

Ringworm in humans generally responds well to treatment. Chances are, if a person hasn’t contracted it from their dog by the time it is diagnosed, it is unlikely that it will occur. 

DIAGNOSIS

There is not a single test to diagnosis ringworm; obtaining an accurate diagnosis of ringworm requires utilizing a few complementary diagnostic tests to confirm the infection and to rule out several other skin conditions that can have a similar appearance. 

* Wood’s lamp examination. A Wood’s lamp is a small hand-held ultraviolet lamp that emits light in a specific range of wavelengths. When they bind to hair shafts, the M.canis fungi produce a chemical reaction that fluoresces a striking, distinct, apple green under the Wood’s light in a darkened room. In many cases, using the Wood’s light uncovers additional sites of infection that were not visible to the eye. 

That said, neither T. mentagrophytes nor M. gypseum fluoresce under a Wood’s lamp, so while the light is useful in establishing a tentative diagnosis, it cannot be used to exclude a ringworm infection.

* Microscopic examination. Since dermatophytes are visible under magnification, your veterinarian can take a sample of hair and skin scrapings for viewing under a microscope to see if any fungal spores are present. About 85% of ringworm infections, regardless of which type of fungus is present, can be confirmed this way. 

* Fungal culture. The most accurate test for diagnosing ringworm in dogs is by fungal culture of a sample of hair or skin cells. The sample is collected from the lesion(s) and placed in a special culture medium where it is monitored for fungal growth. A positive culture can sometimes be confirmed within a couple of days, but in some cases the fungal spores may be slow to grow; culture results can take up to four weeks. Therefore, a suspected sample cannot be deemed negative until four weeks have passed.

* PCR testing. Polymerase chain reaction (PCR) testing is a newer diagnostic technique that can be performed on either tissue or hair samples. These samples are collected by your veterinarian and sent to a lab for processing. This test detects the DNA from any ringworm-causing fungi, providing results in just one to three days. A caveat: The test is highly sensitive and is not able to discern between true disease, contamination from surfaces, and non-viable fungal spores (which can’t cause disease but can be detected in a DNA test). This means that PCR testing is beneficial for making the initial diagnosis, but not helpful in determining whether the infection has resolved and treatment can be discontinued.

TREATMENT

In living hosts, dermatophytes usually remain in superficial tissues such as the skin, hair, and nails, living on the dead top layer of keratin protein. The lesions may be disfiguring and uncomfortable, especially when they are widespread. 

But in rare cases, dermatophytes may go deeper into the body, invading subcutaneous tissues and other sites, especially in immunocompromised hosts. 

Infections in healthy animals are usually self-limiting and may resolve within a few months without therapy.Treatment is recommended anyway, to accelerate recovery, reduce environmental shedding, and decrease the risk of transmission. 

There is not a universal treatment plan for ringworm; your veterinarian will develop a plan based on the severity of the infection, how many pets are involved, whether there are children or other at-risk and susceptible individuals in the household, and how difficult it will be to disinfect your  environment. 

Effective therapy involves elimination of the infection in the dog through use of topical and/or systemic therapies, prevention of further dissemination, and disinfecting and removal of infective materials in the environment.

* Topical treatment. Topical therapy destroys the fungal spores on the lesion itself, thereby limiting environmental contamination and preventing transmission. Topically treated hairs are no longer infectious when they disperse into the environment. Topical therapy is especially important situations where infected dogs can’t be or aren’t confined. 

For generalized dermatophytosis, a twice-weekly, whole-body treatment is recommended. Typical treatments include a lime sulfur (calcium polysulfide) dip (leave-on rinse), an enilconazole leave-on rinse (a broad spectrum antimycotic not available at this time in U.S.), or a miconazole-chlorhexidine rinse/shampoo (this antifungal and disinfectant combination work together to combat the disease). 

For localized treatment, clotrimazole, miconazole, and enilconazole have been shown to be effective, but these are recommended as concurrent treatments, not as sole therapies. Topical treatment may be necessary for a period of several weeks to several months. 

* Systemic therapy. Administration of an oral anti-fungal medication can be an important adjunct to topical therapy, especially for chronic or severe cases. Systemic antifungal therapy targets the active site of fungal infection and spread on the infected dog. 

Effective systemic antifungal drugs include itraconazole, terbinafine, fluconazole ketoconazole, and griseofulvin. While griseofulvin  has been the traditional antifungal drug for decades, its use is not as prevalent as it once was; newer medications appear to be safer and have less side effects. 

Ketoconazole may cause liver pathology and is not recommended as the first-line of attack, but rather reserved for resistant cases. 

Studies have determined that lufenuron (brand name Program) has not proven to be effective in either treating or preventing ringworm infection.

The drawbacks of systemic treatment are the relatively high cost of the drugs and the possibility of toxic side effects, which should be taken into consideration when developing a treatment plan. Dogs receiving any systemic antifungal should be closely monitored and all directions for administering the medications carefully followed. 

ENVIRONMENT THERAPY

Diligent and thorough environmental decontamination is an imperative part of treatment. Without adequate attention to the environment, the infection may not resolve, it can spread, or even cause of reinfection. 

If your pet has been diagnosed with ringworm, dermatophytes are now probably everywhere your dog has been. Infected hairs contain numerous microscopic fungal spores that can be shed into the environment and can survive for almost two years. 

Because infection of other animals and humans can occur, either by direct contact with an infected dog or through contact with fungal spores, you now have to clean and disinfect everything your pet has come into contact with – and continue to do this throughout the treatment period. Yep, it’s a big bummer. But it is an essential part of treatment because affected dogs will continue to reinfect their environment until the infection has resolved completely. 

How often you need to clean and disinfect depends on several factors, including the number of infected individuals, whether the treatment is topical, systemic, or both, and if there any at-risk individuals in the household. Your veterinarian can advise a tailored plan, but it is generally recommended that  twice weekly cleaning includes mechanical removal of hair and washing and disinfection of target areas followed by disinfection. 

As soon as possible following a diagnosis of ringworm, perform an initial thorough cleaning of your entire home, targeting your dog’s favorite spots. Mechanically remove hair, dander, and skin particles from all surfaces. Be aware that vacuuming alone does not decontaminate surfaces, but it does remove infective hair, so vacuum everywhere possible. After vacuuming, dispose of the vacuum bag outside of the home or disinfect the canister immediately. 

Vacuum or use duct tape or lint rollers to remove hair from upholstered furniture. Carpet and rugs can be decontaminated by washing twice with a carpet shampooer with detergent or via hot water extraction. For hard surface floors, use commercial disposable cleaning cloths designed for dry mopping floors (such as Swiffer). Avoid brooms and mops as they are difficult to thoroughly clean and disinfect after use. 

Dust with electrostatic cloths and dispose of immediately after use. Clean all washable surfaces with soap and water. Infective material is easily removed from the environment; if it can be washed, it can be decontaminated. 

Any water temperature and any detergent are sufficient for decontaminating washable textiles (don’t forget to launder your dog’s bedding and toys); two washings on the longest wash cycle are recommended. Wash exposed items separately from non-exposed items and disinfect the appliances afterwards. 

Daily removal of hair from the area where your dog is being confined is recommended.

Proper disinfection is a three-step process: 

1. Mechanically remove all visible debris (hair and skin flakes); disinfectants are not effective in the presence of organic debris. 

2. Wash the target item or surface with a detergent until the area is visibly clean, following with a rinse to remove the detergents, as cleansers some may inactivate disinfectants. 

3. Apply a disinfectant to kill any residual spores. Readily available disinfectants include: 

• Sodium hypochlorite (household bleach). Effective when used at concentrations ranging from 1:10 to 1:100 even with short contact time.

• Enilconazole. Available as a spray or environmental fogger. Relatively expensive. Has limited availability in some countries.

• Accelerated hydrogen peroxide (AHP). A newer broad-spectrum disinfectant that has gained widespread use. Available in concentrates and ready-to-use formulations.

• Rescue (Accel). Another effective broad-spectrum disinfectant. Available in a ready-to-use formula, concentrate, or wipes.

RESOLUTION OF INFECTION

Many dogs will respond fairly quickly to treatment, often showing improvement within a week or two. Full treatment to clear the infection usually takes at least six to 10 weeks but can even last as long as three to four months. 

Do not discontinue treatment as soon as your dog visually appears healed; dogs can still carry infective fungi even after signs appear to have completely resolved. Recurrent or lingering infections tend to be the result of treatment failure, either through inadequate duration of therapy or failure to properly decontaminate the environment. 

Your veterinarian can monitor the healing progress (using a Wood’s light and/or fungal cultures) and use these results to determine when your dog is cured. Following your veterinarian’s recommendations is very important to ensuring a successful outcome and to prevent recurrence.

The good news is that almost all dogs recover completely with no long-term effects (hair loss is not permanent unless the follicle has been destroyed). Humans, on the other hand, may develop a permanent aversion to housecleaning! 

The gut’s primary job is complicated and critical – extracting nutrients from food and moving waste products out of the body – it’s a marvel of engineering. In recent decades, though, we’ve learned that the gut is even more complex and amazing than we previously knew: Researchers have discovered that the bacteria and fungi living in the gut can affect our behavior – or, more significantly to WDJ readers, our dogs’ behavior! 

GUT FEELINGS

The populations of bacteria, viruses, fungi, and microfauna that live on the canine (and human and rodent) body are known as the microbiome. You and your dog host multiple different environments with different populations of tiny beings living on you: on the skin, in the mouth, in the vagina if you’ve got one, and in the gut. 

The gut is a sort of tube running through you, and lining that tube is a dynamic ecosystem of various bacteria, helping digest your food, producing nutrients that you need, and, it turns out, affecting how you feel.

Evidence for a relationship between the gut and behavioral health is strong. Inflammatory bowel disease in humans is associated with anxiety and depression. Autism is associated with gut issues, as are many psychiatric illnesses. Antibiotics can kill off many of the bugs in our gut, and when they do, the risk of developing an anxiety disorder increases. Gut infections can also increase the risk of anxiety disorders. We know that the gut microbiome can affect the stress response, and that this relationship goes both ways – the stress response can also affect the bugs in our gut.

Normal, non-pathological personality traits also seem to change in concert with our gut bacteria. A 2020 study looked at 655 people who filled out online questionnaires and sent in fecal samples. They found decreased gut diversity in participants who reported having high stress levels and those who described themselves as “more conscientious.” Researchers also found increased gut diversity in people with larger social networks. They also identified specific bacterial species associated with people having particular personality traits.

These studies show correlations, that gut and behavioral health go hand in hand. But we still don’t know how this relationship works. Does anxiety cause gut dysfunction? Or does gut dysfunction cause anxiety? 

Studies in laboratory rodents show that fecal transplants (populating one mouse’s gut with the contents of another mouse’s gut) can change the recipient’s behavior to match that of the donor. 

In one study, researchers stressed mice until their behavior changed to demonstrate anxiety. Then they gave an unstressed population of mice fecal transplants from these anxious donor mice. The previously unstressed population began displaying anxiety behaviors, apparently due only to the transplant of bacteria from stressed mice. Fascinating!

GUT REACTION

Okay, okay! Let’s discuss what matters most to us dog owners: Can we alter the bacterial populations in our dogs’ guts to change their behavior? 

We already commonly alter bacterial populations in dogs to promote gut health, either by giving carefully curated commercial probiotic supplements or less carefully curated supplements in the form of foods like yogurt, kefir, or kraut. Could we give probiotics that have not just gut health benefits, but behavioral health benefits, too?

Multiple studies have addressed this question in humans and laboratory rodents. Because a single study is limited in what it can tell us – it’s affected by the exact methods the researchers use, as well as a healthy helping of chance – the best evidence we have is a meta-analysis, a study that summarizes the findings of many other, smaller studies.

A 2018 meta-analysis by Reis et al. looked at a number of studies on the effects of probiotics on behavior in both humans (14 studies) and laboratory rodents (22 studies), and this summary study provides us with our best evidence about whether probiotics really can change behavior.

This meta-analysis pooled the results of all the laboratory animal studies and analyzed them together to see what the overall results were. Overall, probiotics did seem to work to change behavior in mice, but not rats, and then only in mice who were in some way unhealthy or stressed. (Some studies did show effects in rats or unstressed mice, but the overall results suggested that those studies showed effects only by chance.) As for humans, probiotics did not seem to have an effect in us either. 

The researchers had some insights into why studies in rats and humans might have shown no effect (or at least no consistent one), while studies in mice did:

* There may be a baseline of anxiety below which probiotics aren’t going to do much for you – you’re already behaviorally healthy. Surprisingly, none of the human studies included subjects who were actually suffering from anxiety!

* Measuring changes in the feelings of humans is difficult, requiring self-report tests, which are notoriously unreliable. Possibly, the humans taking probiotics did start to feel better but weren’t aware of it. In fact, studies suggest that when you’re coming out of depression or ongoing anxiety, you may start to have measurable improvements before you are consciously aware of them. Measuring changes in behavior in laboratory rodents is more objective, however, and therefore may have been more sensitive.

* Probiotics take time to work. Studies may not run long enough to see real changes; increased time equates to increased expense. Only half of the studies included in this meta-analysis lasted for at least eight weeks. Benefits in humans may have been seen in longer-duration studies.

* Dose may matter. The doses of probiotics given to mice, rats, and humans weren’t all that different, but when the massive differences in size of those species are taken into account, they differed wildly. Since the smallest animals showed the clearest effects, it may be that increasing dose makes probiotics more effective in larger animals.

* The researchers suggested that it’s possible that we need to give humans doses dozens or hundreds of times higher than what we are currently dosing! This suggests that doses in dogs may be low as well.

MARKET THAT HUNCH!

In January 2019, the first probiotic marketed for behavioral change in dogs, Calming Care, was released by Purina. It contains B. longum, strain BL999. (It also has liver in it, and my dogs report that it tastes very good; they lick it right up.) Calming Care is the only behavioral probiotic that has been tested in dogs, though many probiotics for gut (not behavioral) health are on the market.

Calming Care was tested by Purina, but the study was not published in a peer-reviewed journal. Summaries are available, but the detailed methods are not, meaning the specific methods used to test the probiotic aren’t public. This means the study’s results, in classic researcher-ese, are “difficult to interpret” – in other words, something could be confounding the results.

Here’s what we do know: The study involved 24 anxious Labrador Retrievers. For six weeks, dogs were given either B. longum BL999 (i.e., Calming Care) or a placebo; they were then tested for anxiety-like behaviors, heart rate, heart rate variability, and salivary cortisol. (The specifics of the behavior tests are not available.) The dogs were taken off the supplement for three weeks, after which the two groups were switched, and each group received the other treatment (probiotics or placebo) for another six weeks. Both groups were tested a second time. The results were impressive:

* 22/24 treated dogs showed significant reduction in barking, jumping, spinning, and pacing compared to their behavior on placebo.

* 20/24 treated dogs had smaller increases in salivary cortisol (a hormone that is elevated in response to stress) when they exercised and when they were exposed to anxiety inducing stimuli compared to their behavior on placebo.

* 20/24 treated dogs had increased heart rate variability (which is a sign of decreased stress) compared to the behavior on placebo.

REAL WORLD USE

These numbers are very good – surprisingly good in light of the results seen in the meta-analysis discussed earlier. Two vets who prescribe Calming Care for their canine patients reported to me that it seemed to help about half the dogs they tried it on. However, they warned that while it’s worth trying, its effect is not as powerful as a prescription medication in a dog with significant anxiety.

There’s a gap between Purina’s research results and the experience of the two clinicians I know – a gap that could be explained in a few ways. The difference could be accounted for by the objective testing performed by Purina’s researchers, as compared to the owner reports used by the veterinarians. It’s possible that all the Labradors in the Purina study had a biologically similar form of anxiety that responds well to probiotics, but that is seen in only half of the anxious dogs in the real world. Possibly there was a problem with Purina’s study that made its results look better than they really were. The real question is, will Calming Care help your dog?

Probiotics are very safe and unlikely to have negative effects, so it’s worth trying to find out. Purina recommends a trial of at least six weeks before deciding whether the supplement works, but it’s worth running your trial for at least eight weeks.

Some owners want to try behavioral probiotics but don’t want to use Calming Care; some dogs are allergic to liver (one of its ingredients). There are many probiotics marketed for reducing human anxiety; I recommend working with your vet to select one of them. Your best bet will be to pick one containing B. longum (tested in dogs) and/or L. rhamnosus (tested in mice and humans), and not containing L. casei (may increase anxiety).

NO GUTS NO GLORY

Behavioral probiotics can provide a helpful adjunct to behavioral medication, as they did for my anxious dog, whose behavior noticeably improved on Calming Care. Or they can provide a mild effect in dogs who are not on medication. Remember, again, that dogs with serious anxiety issues deserve a visit to a veterinarian who specializes in behavior to discuss medication, as probiotics alone won’t be powerful enough to give them relief.

Our understanding of how the gut microbiome influences behavior is in its infancy. Perhaps in future years we’ll be able to assess a dog’s gut microbiome, predict how it’s influencing their behavior, and tailor a specific probiotic cocktail to push them in the right direction. For now, we’re mostly wandering in the dark. 

However, probiotics are very safe to use and can be something to try when you’re looking for a supplement to help blunt your dog’s anxiety. 

Jessica Hekman, DVM, Ph.D., is a researcher at the Karlsson Lab at the Eli and Edythe L. Broad Institute of MIT and Harvard, studying the genetics of canine behavior. She also teaches online webinars and courses about canine genetics. 

One of the most common skin diseases that develop in dogs is atopic dermatitis. Most of these cases are caused by allergies to substances in the environment. Dog owners are aware of the possibility that their dogs may have environmental allergies to plant pollen and dust or dust mites, but may be completely unaware of one more very significant environmental allergen that can cause ill effect on susceptible dogs: mold.

Molds are a type of multicellular fungi that are present almost everywhere in the environment including the air; favored surfaces include wood, leaves and plants, air ducts, soil, and basements. They thrive in moist, damp, and humid environments, multiplying through microscopic spores that disseminate through the air. Because dogs tend to explore environments – especially with their noses – they can be at increased risk for coming into contact with and inhaling mold spores. 

Molds are usually harmless in small quantities, but they can cause problems if a dog is sensitive to them and suffers an allergic reaction. An allergic reaction occurs when the dog’s immune system responds to a substance with a state of over-reactivity or hypersensitivity. If the allergy becomes chronic, it can become uncomfortable and even painful; if not treated, it can lead to the development of more severe health issues.

Symptoms of mold allergies in dogs

Dogs allergic to mold typically develop a year-round skin problem. If they are allergic to mold, the symptoms may wax and wane with atmospheric humidity (which allows molds to reproduce at a faster rate) but will be present to some extent year-round, because the offending allergen is present all the time, not just seasonally like some pollens. This allergy is most likely to develop in dogs between the ages of 6 months and 3 years, however, dogs can develop an allergy at any time during their lifetime. 

Mold allergies tend to manifest as a skin condition. Symptoms may include scratching (often persistent), inflamed and irritated skin; dry scaly skin, localized or generalized hair loss, chewing/licking (especially the paws); chronic ear infections. It is also possible, but uncommon, for molds to cause respiratory symptoms such as coughing, sneezing, wheezing, labored breathing, discharge from nose and/or eyes, and even loss of appetite and lethargy in more severe cases. Dogs with mold allergies are also frequently affected by other inhalant allergens, such as mites.

Diagnosis

Mold allergies cannot be distinguished from other types of allergies without allergy testing, but your veterinarian may first want to perform a thorough exam, obtain a history, and perform other diagnostics to determine if the presenting condition is caused by or complicated by an infection or another disease that resembles atopic dermatitis. 

Allergy testing in dogs typically takes one of two forms: intradermal skin testing or blood serum testing. Intradermal allergy testing is considered the gold standard for the diagnosis of atopic dermatitis and involves injecting small quantities of 40-60 different types of allergens into the dog’s skin, typically performed under general anesthesia by a veterinary dermatologist. A visible swelling will occur at the injection site if a dog has a reaction to the allergen, allowing determination of which allergens are triggering atopic dermatitis. Blood testing can be performed in a general veterinary practice; a blood sample is drawn from the dog and submitted to a testing laboratory. The lab searches for the presence of antibodies to allergens that are known to contribute to atopic dermatitis. The results of these tests can be used to formulate an allergen-specific immunotherapy based on the offending allergens. 

Management and treatment of mold allergies

The treatment of allergies, including those caused by molds, usually involves two steps: get control and keep control. This frequently requires using one or more therapies, often in combination with one another; these include, but are not limited to, corticosteroids, antihistamines, ATOPICA® (cyclosporine capsules), and Cytopoint® (Lokivetmab). 

Allergen immunotherapy, also known as desensitization or hyposensitization, consists of administering gradually increasing quantities and strengths of relevant allergens, either by subcutaneous injection or sublingual drops. The goal of this treatment is to help build tolerance to the allergens by tempering the immune response. This custom immune-therapy regimen can take up to 12 months before a response is observed. But the commitment may be well worth it as it may not only prevent the current allergies from worsening but also help prevent new allergies from developing.

Dogs suffering from allergies often develop secondary recurrent ear and skin infections. The inflamed skin can be susceptible to bacterial and yeast infections, which in themselves can lead to even more scratching. Targeted topical antimicrobial therapy shampoos and sprays containing chlorhexidine, miconazole, and/or ketoconazole may be recommended, as well as ear cleansers and treatments. In severe cases, oral systemic treatments with drugs such as ketoconazole, itraconazole, or terbinafine may be necessary.

Environmental therapy

Reducing the mold levels in your dog’s environment can help mitigate exposure and thereby reduce allergy symptoms. Unfortunately, because mold is all over, completely avoiding contact is not possible. Ideally, keep your dog (and his bed!) out of damp basements or garages; frequent baths or wipe-downs with a damp microfiber cloth can help remove mold spores that fall on his skin and coat. Inspect your dog’s favorite places, especially under his bedding. Large mold infestations in the home can usually be seen or smelled. If mold is present, these areas should be cleaned and treated appropriately. Depending on the location, extent, and type of mold, this may need to be done by a professional service. 

Because a mold allergy is environmental and environmental allergens are everywhere, complete alleviation of the condition is not usually possible and most dogs will require lifelong treatment.  But it can be successfully managed, resulting in a happier and more comfortable dog.

Photo: Przemysław Iciak/Getty Images