Allergen: A substance that causes an allergic reaction. Anything can be an allergen to a hypersensitive individual, even water. The term has meaning only in relation to an individual who is hypersensitive to that substance.
Allergen-specific immunotherapy: Also known as “allergy shots.” An injection that is custom-made for each patient based on results of intradermal skin tests. The injections contain saline solution and tiny amounts of (commercially produced) extracts from the substances to which the patient is hypersensitive. The injections are given once or twice weekly for four to six months (or longer); the amount of the allergens that the injections contain is slowly increased until a “maintenance dose” is achieved. This therapy is extremely effective, though time-consuming and (over time) expensive.
Allergic contact dermatitis: A hypersensitivity reaction to skin contact with an environmental substance.
Alopecia: Hair loss.
Antibody: Also known as immunoglobulin. A complex Y-shaped protein used by the immune system to identify and neutralize foreign substances. Antibodies are produced by white blood cells.
Antigen: A molecule that induces the formation of antibodies.
Atopy: Also known as “canine atopic dermatitis.” A hereditary and chronic allergic skin disease. Dogs may be allergic to inhaled substances or substances their skin has comes in contact with. Redness and hair loss from scratching is often worst around the eyes, muzzle, ears, and on the feet.
Food hypersensitivity: Also known as “food allergy.” An uncommon, nonseasonal hypersensitivity caused by a dietary substance; an abnormal immunologic response to an ingested substance. Food hypersensitivity is not usually associated with a change in diet. Most dogs who develop the condition have eaten the same food for more than two years. A dog can develop a food allergy to any food, but the most commonly incriminated foods in canine food hypersensitivity include beef, dairy products, lamb, poultry products, wheat, soy, corn, rice, and eggs. (Note that these are also some of the most common ingredients in commercial pet food.)
Intradermal (skin) tests: A test in which tiny amounts of various environmental allergens (such as local tree, grass, and flower pollens) are injected under the dog’s skin, and the skin is observed for a reaction. Redness and swelling indicates a substance to which the dog is allergic. Needed in order to customize a dog’s immunotherapeutic injections (“allergy shots”).
In vitro diagnostic tests: Also known as blood or serologic tests for antigen-induced antibodies, ELISA, or RAST tests. Not very reliable indicators of allergy because of the large numbers of false positive and false negative results.
Pruritus: Itchiness; an unpleasant sensation that causes the desire to scratch.
Pyoderma: A bacterial infection of the skin. Generally treated with antibiotics, but the underlying cause of the infection needs to be addressed, too, so the condition doesn’t recur. The type of antibiotic prescribed will depend on whether the pyoderma originates from deep within the skin or closer to the surface (superficial).
Pyogenic: Bacterial infection that produces pus (dead white blood cells).