ADVERTISEMENT Atopic dermatitis, defined as an allergic reaction to environmental allergens (such as pollens, barn dust, molds, etc.), is probably more common in horses than currently reported. It can be seasonal or, in climates such as California, present year round. The three most common presentations are urticaria (“hives”), urticaria with pruritus (itching), and pruritus alone. Pruritus most commonly affects the face and trunk. Seasonal signs would be most consistent with allergy to pollens; year-round signs would be more consistent with an allergy to molds or barn dust. Urticaria, se...