Diagnosis and treatment of allergies (atopy, food allergy)
A structured work-up of chronic itching: ruling out parasites and infections, an elimination diet, diagnosis of atopy and a choice of treatment that can be maintained for years without steroids.
What it involves
An allergy in a dog or cat is an excessive reaction of the immune system to something that is normally harmless: a protein in food, house dust mites, pollen, moulds or flea saliva. In animals it shows mainly in the skin — itching, redness, paw licking, ear infections — and less often as sneezing or watery eyes, as in people.
Diagnosing an allergy is a process of elimination, not a single test. First we rule out fleas, parasites and infections, then food allergy with an elimination diet, and what remains is atopic dermatitis. Blood allergy tests or intradermal tests are not used to establish an allergy — they are used to choose allergens for desensitisation once the diagnosis has been made.
An allergy cannot be cured, but it can be controlled so that the animal lives without itching. Today we have medications that suppress itching without the side effects of steroids, and immunotherapy (desensitisation), which in some patients reduces the severity of the disease for years.
When it is used
We start allergy diagnosis when itching lasts longer than a few weeks, returns seasonally or after medication is stopped, and basic tests have shown no parasites. The typical patient is a dog between 1 and 3 years of age who has started licking its paws and has recurrent ear infections.
In cats, allergy more often shows as excessive licking (symmetrical hair loss on the belly), small scabs on the back and neck, or lesions around the muzzle and neck.
Indications: symptoms that should prompt a visit
- Your dog licks and bites its paws, and the skin between the toes is red or stained brown by saliva.
- The itching appears every year in spring or summer and goes away in winter.
- Your dog's ears become inflamed again every few weeks despite effective ear-drop treatment.
- Your cat has licked the fur off its belly and the inside of its thighs down to bare skin.
- Your dog scratches all year round, and flea preparations and skin scrapings have shown nothing.
- Redness and itching appeared after a change of food, or are accompanied by loose stools and flatulence.
- Your dog has recurrent bacterial skin infection (pyoderma) that clears up with an antibiotic and then comes back.
Conditions for which we use it in particular
Diagnostics beforehand
Before we diagnose an allergy, we carry out skin scrapings, cytology and a trichogram in the consulting room (on-site laboratory), put full flea prevention in place for all the animals in the household, and treat secondary infections. Without this stage, any further diagnosis is unreliable.
Next we run an elimination diet for 8 weeks: a food with a single protein new to the animal, or a hydrolysed food, without any other treats, scraps or flavoured medications. If the itching subsides and returns when the previous food is reintroduced (a challenge) — it is a food allergy. If it does not subside, we diagnose atopy. When planning desensitisation we carry out allergy blood tests (sent away); we add hormone tests when the picture suggests an endocrine cause.
How it proceeds
Diagnosis is a series of visits spread over 2–4 months. At the first we agree a plan, carry out basic tests, treat infections and start a medication that eases itching, so that the animal does not suffer during the search. At the second (after 2–4 weeks) we check the skin, repeat cytology and — if the skin is clean — start the elimination diet with precise instructions on what is and is not allowed.
After 8 weeks of the diet we assess the effect and carry out a challenge. With a diagnosis in hand we choose long-term treatment: for food allergy, an appropriate diet; for atopy, a combination of anti-itch medications (tablets or an injection that works for several weeks), skin barrier restoration (baths, fatty acids) and, possibly, immunotherapy based on allergy tests. We run treatment with check-ups every 3–6 months.
Aftercare
During an elimination diet the most common cause of failure is a single treat “once a day” — make sure everyone at home, including children, knows this. Keep an itch diary on a scale of 0–10; it helps to assess progress objectively. Continue flea prevention all year round.
With atopy we check the skin and ears every 3–6 months, and with long-term medication we periodically carry out a full blood count and biochemistry. Call if severe itching suddenly returns, pustules or an ear infection appear, or there are side effects of medication (vomiting, diarrhoea, drowsiness).
Frequently asked questions
Can't we simply do allergy blood tests?
Blood tests detect antibodies to environmental allergens, but they also come out positive in healthy dogs, and they are unreliable for food allergy. We use them to select the allergens for desensitisation once a diagnosis has been made, not to make the diagnosis.
How long does an elimination diet last, and does it have to be a veterinary food?
A minimum of 8 weeks with no deviations. It may be a hydrolysed food or a home-prepared diet with a single protein the animal has never eaten — we decide this individually. “Hypoallergenic” foods from a shop are usually unsuitable, because they contain trace proteins.
Will the allergy go away with age?
Atopy usually stays with the animal for life, although its severity varies. The aim of treatment is comfort without side effects, and in some patients desensitisation really does reduce the need for medication.
Are anti-itch medications safe for years?
Modern medications (those that block the itch signal in cells, or monoclonal antibodies) have a much better safety profile than steroids. We monitor the patient and blood tests at set intervals to confirm that safety.
We manage every case individually. The scope, indications and course described above are indicative; we agree the exact diagnostic and treatment plan during the consultation. This content is for information only and does not replace a veterinary consultation.
Have questions about diagnosis and treatment of allergies?
Call us or book a consultation. We will set out the diagnostic and treatment plan in writing, before you decide.