Food allergy or intolerance in dogs

Recognise the signs

• Chronic or recurring itching — often year-round (unlike seasonal environmental allergy), affecting ears, paws, armpits, groin, face, and around the eyes
• Recurring ear infections (otitis externa) — often with dark, waxy discharge; may affect one or both ears
• Recurring skin infections (pyoderma) — red, angry skin, pustules, crusting
• Paw licking and chewing — red, stained paw fur from saliva
• Facial rubbing on furniture or carpet
• Vomiting — chronic or intermittent, not related to eating grass or scavenging
• Diarrhoea or loose stools — sometimes with mucus; more common with food intolerance than true allergy
• Increased frequency of bowel movements
• Anal sac problems — scooting or anal sac impaction secondary to gut inflammation
• Poor coat condition, dull fur, dandruff

First aid steps

1. 1. Keep a food diary — record everything the dog eats including treats, supplements, flavoured medications, and dental chews. Note any correlation between diet changes and symptom flare-ups.
2. 2. Photograph the dog's skin, paws, and ears to document the condition and track progress over time.
3. 3. Book a veterinary appointment — the vet will rule out other causes (parasites, environmental allergy, infection) before recommending a dietary trial.
4. 4. Do not start a dietary trial without veterinary guidance — an improperly conducted trial produces unreliable results and delays diagnosis.
5. 5. Do not give antihistamines or steroids without veterinary advice — short-term relief masks symptoms and makes diagnosis harder.
6. 6. Avoid switching foods randomly — this does not constitute a proper exclusion diet and may make allergy testing more difficult.
7. 7. If the dog is scratching severely, check for fleas first (flea allergy dermatitis is far more common than food allergy and is the most important differential).
8. 8. Ensure all family members understand that during a dietary trial, no treats, table scraps, or flavoured products of any kind can be given — even a single exposure to the allergen invalidates the trial.

While transporting to the vet

• Food allergy does not require emergency transport. Standard precautions for a comfortable car journey apply.

When it can usually wait

• Mild, intermittent itching without skin damage or infection — book a routine vet appointment.
• Occasional loose stools without blood or significant frequency — monitor and book a routine appointment.
• Mild paw licking without hair loss — note and mention at the next routine vet visit.

Common causes

• True food allergy (immune-mediated, IgE and non-IgE mediated) — the immune system reacts to a protein in the food
• Food intolerance (non-immune, digestive) — the digestive system cannot properly process a food component
• Most common allergens in UK dogs: beef, dairy products, wheat/gluten, chicken, lamb, egg, soy, fish
• Novel proteins can also become allergens if fed long-term
• Additives, colourings, and preservatives — occasionally implicated but less common than protein allergens
• Overlap with environmental allergy (atopy) — many dogs have both simultaneously, complicating diagnosis

What the vet will need to know

• Full dietary history including all brands, flavours, treats, and supplements given
• Age of onset and duration of symptoms
• Whether symptoms are year-round or seasonal (year-round suggests food; seasonal suggests environmental allergy)
• Any pattern relating symptoms to specific foods or diet changes
• Which body areas are affected — distribution pattern helps differentiate food allergy from atopy
• History of ear infections and what treatment was used
• Has the dog ever had a skin scraping, skin cytology, or allergy testing?
• Any current or recent medications including flea treatment

Aftercare

• If the dietary trial confirms food allergy (symptoms resolve during the trial and return upon food challenge), the dog will need a long-term diet avoiding the identified allergen(s).
• Some dogs can be managed on commercial diets that avoid known allergens; others require prescription hydrolysed diets long-term.
• Your vet may refer to a veterinary dermatologist for intradermal allergy testing if environmental allergy is also suspected.
• Secondary infections (skin pyoderma, ear infections) will be treated with antibiotics and/or antifungals — these do not resolve with diet change alone and need specific treatment.
• Omega-3 fatty acid supplementation (fish oil) can support skin barrier function — discuss dose with your vet.
• Regular follow-up is important to monitor for new allergen sensitisation over time.

Prevention

• There is no guaranteed way to prevent food allergy, but feeding a varied diet from puppyhood may reduce sensitisation risk (emerging evidence).
• Avoid feeding the same protein source exclusively for years — variety may reduce the likelihood of developing an allergy to a single protein.
• Read ingredient labels carefully when purchasing food or treats.
• Ensure all household members know what the dog is and is not allowed to eat.
• Use plain, ingredient-simple treats during any dietary trial.
• Discuss long-term dietary planning with your vet, particularly if the dog has a breed predisposition to skin conditions.

Breed-specific notes

• West Highland White Terriers — significant predisposition to both food allergy and atopy; skin problems are very common.
• Labrador and Golden Retrievers — overrepresented for food allergy and atopic dermatitis.
• Cocker Spaniels — prone to recurrent ear infections which may have an allergic basis.
• German Shepherd Dogs — higher incidence of food-responsive enteropathy and skin conditions.
• Boxers and French Bulldogs — predisposed to skin-fold dermatitis and atopy which can mimic or co-exist with food allergy.
• Shar-Peis — predisposed to recurrent skin infections and allergic skin disease.

Frequently asked questions

Related topics

• Allergic reaction in dogs
• Dog vomiting — when to worry
• Dog with diarrhoea — when to worry
• Dog has fleas