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A closer look at atopic dermatitis
Atopic dermatitis (often shortened to atopy, or called environmental allergies) is one of the most common skin diseases in dogs. Affected dogs have an inherited tendency to react to ordinary things in their environment, such as tree, grass and weed pollens, house dust mites, moulds and dander, with inflammation of the skin. The main symptom is itch, and itch drives everything else: licking, chewing, scratching, broken skin and infection.
Part of the problem is the skin itself. Dogs with atopic dermatitis have a weaker skin barrier, so allergens get in more easily and the skin loses moisture faster. Inflamed skin is also easier for yeast and bacteria to colonise, which is why so many allergic dogs have repeated skin and ear infections.
Signs usually first appear between about six months and three years of age. At first they may be seasonal (worse in spring or autumn), but in many dogs they become year-round. In warm, humid places such as the Texas Gulf Coast, pollen and mould seasons are long, and many allergic dogs itch for most of the year.
Risk factors
- Genetics. Atopic dermatitis runs in families and is more common in certain breeds, including West Highland White Terriers, Labrador and Golden Retrievers, French Bulldogs and Bulldogs, Boxers, German Shepherds, Shih Tzus and many terriers.
- Young adulthood. Most dogs show their first signs before age three.
- Climate and home. Long pollen seasons, humidity, dust and mould increase exposure.
- Other itch at the same time. Fleas or a food allergy add to the itch, pushing a dog over its “itch threshold”. This is why controlling fleas matters so much in allergic dogs.
Causes
The underlying cause is a combination of genes, a faulty skin barrier and an immune system that overreacts to harmless substances. Common triggers include:
- Pollens from trees, grasses and weeds
- House dust mites and storage mites
- Mould spores, indoors and out
- Dander from people and other animals
Flare-ups are often made worse by secondary infections with bacteria (usually Staphylococcus pseudintermedius) and yeast (Malassezia), which are themselves itchy.
Signs
- Licking and chewing the paws; reddish-brown staining of light fur from saliva
- Rubbing the face and muzzle on furniture or the carpet, or pawing at the eyes
- Scratching the armpits, belly, groin and inner thighs
- Scooting or licking around the rear end
- Repeated ear infections: head shaking, red ears, smelly discharge
- Red skin, small bumps, scabs and hair loss in the itchy areas
- Over time: darkened, thickened, greasy or elephant-like skin, and a yeasty smell
- Hot spots (painful, wet, rapidly spreading patches)
The pattern matters. Itch focused on the paws, face, ears, armpits, belly and rear end is typical of atopic dermatitis and food allergy. Itch concentrated over the lower back and base of the tail points more towards fleas.
How vets diagnose atopic dermatitis
There is no single test that proves a dog has atopic dermatitis. Instead, your vet builds the diagnosis by ruling out the other causes of itch:
- History and examination: when the itch started, whether it is seasonal, where on the body it is worst, and how the dog responded to any past treatment.
- Parasite control: skin scrapings or tape tests for mites, and a period of strict, effective flea control for every pet in the home.
- Checking for infection: tape or swab cytology of the skin and ears to look for bacteria and yeast, which are treated before the underlying itch can be judged.
- An elimination diet trial: about eight weeks on a prescription hydrolysed or novel-protein diet, with nothing else to eat, to rule out food allergy.
- Allergy testing: once atopic dermatitis is diagnosed, intradermal skin testing or blood (serum) testing identifies which allergens to include in immunotherapy. The tests are tools for treatment, not for diagnosis.
Treatment
Most dogs do best with a combination of treatments, adjusted over time. Your vet will tailor the plan to your dog.
Fast itch relief
- Targeted anti-itch medicines. Modern prescription options include oral tablets that block the itch signal and injectable antibody treatments that neutralise a key itch messenger for about a month at a time. They work quickly and have changed how well most allergic dogs can be controlled.
- Corticosteroids: effective and inexpensive for short-term control of flares, but long-term use has side effects, so vets use the lowest effective dose for the shortest time.
- Ciclosporin: an immune-modulating medicine for long-term control, which takes a few weeks to reach full effect.
Treating the skin
- Medicated shampoos and mousses to remove allergens, calm the skin and control yeast and bacteria
- Treating infections with topical products, and oral antibiotics or antifungals when needed
- Skin barrier support: omega-3 fatty acids and some topical barrier products may help over time
Allergen immunotherapy
Often called “allergy shots”, or drops under the tongue, immunotherapy slowly retrains the immune system using small, increasing amounts of the allergens a dog reacts to. It takes several months to a year to show its full effect and helps a majority of dogs to some degree. It is the only treatment that targets the allergy itself rather than the symptoms.
Reducing exposure
Wiping paws and the belly after walks, regular bathing, washing bedding, and good dust-mite control at home can reduce the allergen load, though they rarely control signs on their own.
Recovery and outlook
Atopic dermatitis is usually lifelong, and there will be good months and bad months. With a plan that controls itch, prevents infections and treats flares early, most dogs live comfortable, normal lives. Expect a few months of adjustment at the start, and regular check-ins with your vet to keep the plan working as seasons and needs change.
Prevention and day-to-day care
- Keep up year-round flea prevention for every pet in the home.
- Act early on flares. Ask your vet for a written plan for what to do when itch returns.
- Check the ears and paws weekly and book a visit at the first sign of infection.
- Bathe and wipe as your vet recommends, especially in pollen season.
- Do not breed from dogs with atopic dermatitis, as it is strongly inherited.
Atopic dermatitis or food allergy?
The two look almost identical: itchy paws, face, ears, armpits and rear end, with repeated ear and skin infections. Some clues point one way or the other, but only a diet trial can tell them apart:
| Atopic dermatitis | Food allergy | |
|---|---|---|
| Trigger | Pollens, dust mites, moulds | An ingredient in the diet, usually a protein |
| Seasonal? | Often, at least at first | No: the same all year |
| Age at first signs | Usually 6 months to 3 years | Any age, including under 6 months and in older dogs |
| Gut signs | Uncommon | Some dogs have soft stools or frequent bowel movements |
| How it is confirmed | By ruling out other causes | An 8-week elimination diet trial, then re-challenge |
Some dogs have both. A dog whose itch improves on a diet trial but does not disappear may have a food allergy and atopic dermatitis together.
Doing a diet trial properly
A diet trial only works if it is strict. For about eight weeks your dog eats only the prescription diet your vet chooses, usually a hydrolysed protein diet (proteins broken into pieces too small to trigger the immune system) or one with a protein your dog has never eaten.
- No treats, chews, table scraps or flavoured medicines unless your vet approves them.
- Tell everyone in the household, including children and visitors.
- Watch out for dropped food and other pets’ bowls.
- Keep a simple itch diary, scoring the itch from 0 to 10 each week.
If the itch improves, your vet will usually ask you to re-introduce the old food. If the itch returns within days, that confirms a food allergy.
What treatment costs over time
Atopic dermatitis is a long-term condition, so it helps to think in terms of yearly costs rather than single visits. The main costs are vet visits for flares and infections, ongoing anti-itch medication, medicated shampoos, and, for some dogs, allergy testing and immunotherapy. Costs depend heavily on your dog’s size, since many medicines are dosed by weight. Ask your vet to compare options: for some dogs immunotherapy reduces the need for other medication over time. Pet insurance taken out before signs appear usually covers allergic skin disease.
Questions to ask your vet
- How sure are you that this is atopic dermatitis, and what have we ruled out?
- Should we do a diet trial first? Which diet, and for how long?
- Which anti-itch treatment fits my dog and our budget, and what are the side effects?
- Is there an infection now, and how will we know when it has cleared?
- Would allergy testing and immunotherapy help my dog?
- What should I do at home when a flare starts?
- Would seeing a veterinary dermatologist help?
Living with an allergic dog
Most owners find that a routine makes the biggest difference: a monthly check-in on how the itch is going, a plan agreed with the vet for flares, a regular bathing day, and an eye on the ears and paws. Keep notes of when signs flare. Over a year or two the pattern (spring pollen, autumn weeds, damp winters) helps you and your vet start treatment before your dog is miserable.