The most common symptoms are dermatological or gastrointestinal (or a combination of both). The dermatological signs are varied, and are often indistinguishable from those associated with atopic dermatitis. When pruritus is not responsive to corticosteroids, a food allergy should be considered. However, if pruritus responds to corticosteroids, that does mean that no food allergy is present.

Generalised or localised non-seasonal pruritus (of the face, ears, paws, armpits, inguinal and perineal regions) is the most frequently described symptom. The patient experiences severe itching, resulting in excessive and unnatural scratching, biting and licking.

It is also possible for the effects of a food allergy to be below the “itch threshold”, with only flare-ups of pruritus occurring when there are increased levels of environmental allergens during the high-pollen season. Otitis externa and recurrent pyoderma, with or without pruritus, has also been associated with food allergies.

Gastrointestinal symptoms may include vomiting, diarrhoea, weight loss, abdominal discomfort, flatulence and frequent defecation (more than three times a day).