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Dermatologic Food Reactions in Cats

While the pathogenesis of dermatologic food reactions is not fully understood, immediate reactions and delayed reactions to food are thought to be due to a hypersensitive immune response. Dermatologic food reactions are non-seasonal reactions which occur following ingestion of one or more allergy causing substances in an animal’s food. The physical reaction is frequently excessive itchiness, with resultant excessive scratching at the skin.

On the other hand, food intolerance is a non-immunologic idiosyncratic reaction due to the metabolic, toxic or pharmacologic effects of the offending ingredients. Since it is not easy to distinguish between immunologic and idiosyncratic reactions, any negative response to food is generally referred to as an adverse food reaction.

Symptoms and Types

• Non-seasonal itchiness of any body location
• Poor response to anti-inflammatory doses of glucocorticoids suggests food hypersensitivity
• Vomiting
• Diarrhea
• Excessive gut sounds, passing of gas, and frequent bowel movements
• Malassezia dermatitis (fungal skin infections), pyoderma (bacterial skin infections), and otitis externa (inflammation of the outer ear)
• Plaque – broad, raised flat areas on the skin
• Pustule – pus-containing raised skin inflammation
• Erythema – redness of the skin
• Crust – dried serum or pus on the surface of a ruptured blister or pustule
• Scale – flakes or plates of dead skin
• Self-induced baldness due to scratching
• Abrasion/sores on the skin due to scratching
• Leathery, thick, bark-like skin
• Hyperpigmentation – darkening of the skin
• Hives – swollen or inflamed bumps on the skin
• Giant wheals (elongated marks) on the skin
• Pyotraumatic dermatitis – bacterial infection of skin wounds due to scratching excessively                       

Causes

• Immune-mediated reactions – result of the ingestion and subsequent presentation of one or more glycoproteins (allergens) either before or after digestion; sensitization may occur as the food passes into the intestine, after the substance is absorbed, or both
• Non-immune (food intolerance) reactions – resulting from ingestion of foods with high levels of histamine (an antigen known to cause immune hypersensitivity) or substances that induce histamine either directly or through histamine-releasing factors
• It is speculated that in juvenile animals intestinal parasites or intestinal infections may cause damage to the intestinal mucosa, resulting in the abnormal absorption of allergens and subsequent sensitization to some ingredients