A Guide to Dog Allergy Medications

There are many medications available to help relieve the symptoms associated with allergies in dogs. Learn more about what medications you can give your dog to relieve his allergy symptoms.

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There are several manifestations of allergies in dogs, including atopic and flea allergy dermatitis, allergic rhinitis and bronchitis, hives, and insect bite hypersensitivity. Symptoms may include pruritus (itchiness), sneezing, coughing, clear nasal discharge, or raised welts on the skin.

Pruritus due to hives and insect bite hypersensitivity are caused by the release of histamine and other inflammatory mediators. Over-the-counter dog allergy medications like antihistamines are typically effective at relieving this form of itchiness. More severe cases may require the addition of a glucocorticoid to reduce inflammation.

Using Glucocorticoids to Treat Atopic Dermatitis

There was a time when glucocorticoids were the primary form of treatment in relieving pruritus (itchiness) associated with atopic dermatitis. Glucocorticoids are effective for this purpose but come at a price.

Glucocorticoids may increase your dog’s thirst and hunger. When they drink more water, they naturally have to urinate more often. This can lead to urinary accidents in the house. They may pant for no apparent reason and act lethargic.

Long-term chronic use of glucocorticoids can cause thinning of the skin and haircoat. Dogs may develop comedones (black heads) of their skin, particularly on the underside of their belly. Wounds may take longer to heal. Muscle wasting may occur because of catabolic changes to their metabolism. Dogs may become obese due to increased appetite and caloric intake. There is an increased risk of developing bacterial or fungal infections, adult-onset demodectic mange, and diabetes mellitus.

Today, there are many alternative and equally effective medications that relieve the pruritus associated with atopic dermatitis. These medications are generally safer than glucocorticoids when used long-term. However, there may still be instances when glucocorticoids are an appropriate choice to manage pruritus.

The following principles should be followed when using a glucocorticoid to treat your dog’s pruritus:

  1. Any underlying disease that is contributing to your dog’s pruritus should be identified and treated. Using a glucocorticoid without completing a diagnostic workup first can mask an underlying disease and make your dog’s overall condition worse.
  2. The least potent glucocorticoid should be used at the lowest effective dose for the shortest amount of time necessary to control your dog’s symptoms.
  3. Your dog should be rechecked by your veterinarian at regular intervals while taking a glucocorticoid.

Allergic rhinitis and bronchitis may be responsive to the antihistamine cetirizine (commonly known as Zyrtec). Coughing due to allergic bronchitis may require an antihistamine and glucocorticoid combination, such as trimeprazine and prednisolone (Temaril-P).

Itchy skin associated with atopic and flea allergy dermatitis is not always responsive to antihistamines. Medications that target specific itch receptors in the skin may provide dogs with more complete relief from their pruritus than antihistamines. See the article “Allergies in Dogs” (WDJ website) for more information on other treatments that may help your dog.

The following is an information guide to many of the common medications that are used to treat allergy symptoms in dogs.

Cetirizine

Common trade name: Zyrtec

Drug class: Antihistamine (non-drowsy)

Indicated for: Hives, insect bite hypersensitivity, allergic rhinitis and bronchitis. Not shown to be effective for atopic dermatitis.

Contraindications: None.

Potential side effects: Vomiting, hypersalivation

Formulations available: Available over-the-counter as tablets, chewable tablets, oral solution, and gel capsules. Avoid using oral disintegrating tablets as this formulation may contain xylitol which is a known toxin in dogs. Avoid using combination products that contain pseudoephedrine.

Clemastine

Common trade name: Dayhist

Drug class: Antihistamine

Indicated for: Hives, insect bite hypersensitivity, atopic dermatitis

Contraindications: Use with caution in dogs with glaucoma or heart disease and in male dogs with an enlarged prostate.

Potential side effects: Lethargy, hyperexcitability, dry mouth

Formulations available: Available over-the-counter as tablets and oral solution.

Chlorpheniramine

Common trade name: Chlor-trimeton

Drug class: Antihistamine

Indicated for: Hives, insect bite hypersensitivity, atopic dermatitis

Contraindications: Should be used with caution in dogs that have glaucoma, high blood pressure (hypertension), or heart disease.

Potential side effects: Lethargy, diarrhea, vomiting, constipation, loss of appetite, dry mouth

Formulations available: Available over-the-counter as tablets. Avoid using extended-release tablets as this formulation may contain sodium benzoate, a known toxin in dogs. Avoid using any of the available syrups as these formulations may contain other ingredients, including decongestants, acetaminophen (Tylenol), or antitussives, as these other ingredients may be toxic to dogs.

Diphenhydramine

Common trade name: Benadryl

Drug class: Antihistamine

Indicated for: Hives, insect bite hypersensitivity, atopic dermatitis. May prevent motion sickness or vomiting. Sometimes used as a sedative.

Contraindications: Should be used with caution in dogs that have glaucoma, high blood pressure (hypertension), heart disease, or seizures.

Potential side effects: Lethargy, constipation, dry mouth. Some dogs may experience paradoxical excitability rather than sleepiness.

Formulations available: Available over-the-counter as tablets, capsules, chewable tablets, gelcaps, liquid, elixir, and syrup. Also available as an injection for veterinary use only. Some liquid, elixir, and syrup formulations contain alcohol, which is toxic to dogs. Avoid using any formulation that contains other ingredients, including decongestants, acetaminophen (Tylenol), or antitussives, as these other ingredients may be toxic to dogs.

Fexofenadine

Common trade name: Allegra

Drug class: Antihistamine

Indicated for: Although this is an antihistamine, there is limited research to support its use in dogs.

Contraindications: Should be used with caution in dogs with the MDR-1 mutation. Other contraindications are not known due to limited research on the use of this medication in dogs.

Potential side effects: Lethargy, diarrhea, vomiting

Formulations available: Available over-the-counter as tablets, gelcaps, and suspension. Avoid using oral suspension as this formulation contains xylitol, a known toxin in dogs. Avoid using any of the formulations that contain other ingredients, including decongestants.

Hydroxyzine

Common trade name: Atarax, Vistaril

Drug class: Antihistamine

Indicated for: Hives, insect bite hypersensitivity, atopic dermatitis. Sometimes used as a sedative.

Contraindications: Should be used with caution in dogs that have glaucoma, high blood pressure (hypertension), heart disease, or seizures.

Potential side effects: Lethargy, constipation, dry mouth, tremors, seizures. Some dogs may experience paradoxical excitability rather than sleepiness.

Formulations available: Tablets, capsules, and syrup. All formulations require a prescription. Also available as an injection for veterinary use only.

Trimeprazine/Prednisolone

Common trade name: Temaril-P

Drug class: Antihistamine and corticosteroid

Indicated for: Atopic dermatitis, coughing

Contraindications: Should not be used in dogs with systemic fungal infections. Should be used with caution in dogs that have high blood pressure (hypertension), heart disease, kidney disease, liver disease, stomach ulcers, corneal ulcers, hyperadrenocorticism (Cushing’s disease), diabetes mellitus, or congestive heart failure. Should be used with caution in puppies.

Potential side effects: Lethargy, low blood pressure, cardiac arrhythmias, and development of hyperadrenocorticism with long-term use.

Formulations available: Tablets by prescription only.

Oclacitinib

Common trade name: Apoquel

Drug class: JAK inhibitor

Indicated for: Atopic dermatitis, flea allergy dermatitis. May also be helpful at managing some auto-immune disorders (such as pemphigus or cutaneous lupus). May help relieve pruritus associated with sarcoptic mange.

Contraindications: Should not be used in dogs less than 12 months old. Should not be used in pregnant or nursing dogs or in dogs intended for breeding. Should be used cautiously or not at all in dogs that currently have cancer or a serious infection of any kind.

Potential side effects: Vomiting, diarrhea, and loss of appetite can be seen in some dogs—these side effects typically resolve quickly on their own. May increase susceptibility to infections. Dogs with a history of urinary tract infections (UTIs) may experience an increased occurrence of UTIs.

Formulations available: Tablets and chewable tablets by prescription only.

Lokivetmab

Common trade name: Cytopoint

Drug class: Monoclonal antibody

Indicated for: Atopic dermatitis, flea allergy dermatitis

Contraindications: No known contraindications.

Potential side effects: Vomiting, diarrhea, lethargy, pain at the injection site, loss of appetite, or lameness can be seen in some dogs—these side effects typically resolve quickly on their own.

Formulations available: Injection for veterinary use only.

Cyclosporine

Common trade names: Atopica, Cyclavance, Neoral, Gengraf

Drug class: Immunosuppressive

Indicated for: Atopic dermatitis. Also used off-label for the treatment of some immune-mediated diseases.

Contraindications: Should not be used in puppies less than six months old. Should not be used in dogs with malignant cancer or that have a history of malignant cancer. Should be used with caution in dogs with diabetes mellitus or kidney disease.

Potential side effects: Vomiting, diarrhea, or loss of appetite can be seen in some dogs—these side effects typically resolve quickly on their own. May increase susceptibility to infections. Other side effects that have been seen in dogs include gingival hyperplasia (increased growth of the gums), development of diabetes mellitus, excessive fur growth or shedding, and small benign skin growths. Liver damage and blood clots are rare side effects. Dogs with a history of urinary tract infections (UTIs) may experience an increased occurrence of UTIs.

Veterinary formulations available by prescription: Capsules (Atopica) and oral solution (Cyclavance)

Human formulations that can be used in dogs by prescription: Capsules (Neoral, Gengraf) and oral solution (Neoral)

Human formulation that should NOT be used in dogs: Sandimmune (capsules and oral solution). This formulation is not bioequivalent to the other formulations available and should not be used in dogs.

Prednisone/Prednisolone, Methylprednisolone, and Dexamethasone

Common trade name: Prednisone/prednisolone has no common trade name and is available as a generic drug. Methylprednisolone may be known as Medrol, Depo-Medrol, or Solu-Medrol. Dexamethasone may be known as Azium or Dexasone.

Drug class: Glucocorticoid

Indicated for: Inflammatory conditions including atopic dermatitis, flea allergy dermatitis, hives, insect bite hypersensitivity, and allergic rhinitis and bronchitis. Also used for many other conditions, including hypoadrenocorticism (Addison’s disease), immune-mediated diseases (such as immune-mediated hemolytic anemia), and cancer (such as lymphoma).

Contraindications: Should not be used in dogs with systemic fungal infections, viral infections, hyperadrenocorticism (Cushing’s disease), corneal ulcers, or gastrointestinal ulcers. Should be used with caution in dogs with congestive heart failure, high blood pressure (hypertension), liver disease, or kidney disease.

Potential side effects: Increased thirst, hunger, and urination. May also cause panting and lethargy. See sidebar for potential long-term side effects.

Formulations available: Prednisone and prednisolone are available as tablets and oral syrups/solutions. Many oral syrups/solutions contain alcohol and should be avoided in dogs. Methylprednisolone is available as tablets and as an injection for veterinary use only. Dexamethasone is available as tablets, oral solution, and as an injection for veterinary use only. All formulations require a prescription.

The Difference Between Prednisone and Prednisolone

Many drugs are metabolized in the body and converted to both active and inactive forms. Prednisone is converted by the liver into the active metabolite prednisolone. Humans and healthy dogs are readily able to make this conversion, so most pharmacists treat prednisone and prednisolone as bioequivalent drugs. They do not know that there is a difference between prednisone and prednisolone in veterinary patients. Dogs that have liver disease may not be able to readily make this conversion—these dogs may be prescribed prednisolone instead of prednisone. Incidentally, healthy cats and horses are not efficient at this conversion and should be prescribed prednisolone instead of prednisone. If your veterinarian has specifically prescribed prednisolone for your dog, it may be up to you to ensure that your pharmacist has filled the correct medication.

5 COMMENTS

  1. Is there a reason that Apoquel isn’t on the list? I have been using that daily to help with my 4 year old Scottie’s horrendous fungal infection and itching. She still gets it every day as maintenance…

  2. My French Bulldog, color = mostly white – named Frenchi.
    Veterinarians call her a = LWID “little white itchy dog’s” built low to the ground & picking up all ground debris-
    Frenchi spends much time “scratching or licking, underarms, feet, thighs, & private parts.
    She was allergy tested & results point to “environmental-grass,trees”. I was feeding Stella & Chewy Skin & Coat. I was also using Apoquel 5.4mgs -dose for 20# French Bulldog once per day.
    My Vet decided to try Cytopoint, a “Canine Allergic Dermatitis immunotherapeutic”.!!
    Frenchi was injected this past Thursday afternoon- I was amazed- she slept when we returned home.
    Normally she sleeps on bed with my other French Bulldog & my husband. My job is to keep Frenchi from scratching & licking by keeping her busy & entertained.
    Today is Sunday- she is 85-90% cured.
    The few times she decided to lick or chew her body, I believe it was HABIT= not need.
    I am extremely impressed – I am using Cyto & stopped Apaquel. 🐶. Interested in hearing your results.
    Ileen Green, CPDT-KA

  3. Diana pawPrints developed an allergy between 2 and 3 years old. My previous dog had a food allergy and I just eliminated all chicken from is diet and he was fine. Diana was so bad she was losing hair and had skin infections, bumps and sores before the vet diagnosed her. She was put on antibiotics, anti itch meds and Chlorhexadine shampoo. She cleared up but symptoms returned the following Spring. The vet said it is an environmental allergy. I caught it early and have been able to manage it with Benedryl and Chlorhexadine shampoo, both over the counter. The vet said the Benedryl, even at 8 per day, was cheaper than the prescription meds and fine as long as it was working for her. I’ve been tracking pollen counts for two years through the Accuweather app and have determined it is tree pollen. She doesn’t react to grass , mold, weeds or ragweed but when tree pollen is high, that is when she started to itch. So I keep my eye on the weather and as soon as the tree pollen starts to show on the weather app I start the pills and she starts getting bathed more often. Weekly at it’s worst. So far so good.

    Freyja doesn’t seem to be allergic to anything but she is sensitive to pork so no pig ears for her.