Atopic dermatitis in dogs: itching, tests and long-term care

Overview

Not every itchy dog has atopy. It is a condition in which a susceptible dog's skin and immune system react abnormally. Environmental allergens, meaning substances that cause an allergic reaction, can trigger signs. Common examples include pollens, moulds and dust mites. It is not always possible to remove these substances completely from your dog's everyday life.

Signs may occur only in a particular season, all year round, or throughout the year with seasonal flare-ups. The same dog may therefore need different treatment at different times. The aim is good quality of life and a manageable daily routine, rather than simply improving the skin's appearance. Itching can be significant even when the skin still looks fairly normal.

Atopy is estimated to affect 10–15% of dogs. Seasonal itching is reported in 40–75% of cases. Signs that are seasonal at first may later become year-round.

Causes

The outermost layer of skin normally provides protection against the environment. In an atopic dog, this barrier function may be inadequate. When an allergen comes into contact with the skin, the immune system triggers an inflammatory response.

Skin nerves and inflammatory signalling also contribute to itching. For example, IL-31 is a signalling substance involved in itching that some medicines target. There are therefore several different medicine options for controlling itch.

Bacterial and yeast overgrowth can intensify existing skin inflammation. Other allergic diseases can also occur alongside it.

Allergens are proteins to which a sensitised body reacts. Sensitisation produces IgE antibodies, which attach to cells including mast cells in the skin. When the same allergen is encountered again, these cells release histamine and other substances that promote inflammation.

Sometimes a disease resembles atopic dermatitis even though IgE sensitisation is not detected. This is called atopic-like dermatitis.

Risk factors

Atopy usually begins between 6 months and 3 years of age. No clear difference in susceptibility between the sexes is known.

Susceptible breeds include Labrador Retrievers, Golden Retrievers, Boxers, Shar Peis and West Highland White Terriers. Crossbreed dogs also develop atopy.

Atopy is diagnosed more often in dogs whose parents are both atopic. Living mainly indoors is also a historical feature compatible with atopy that contributes to the overall diagnostic assessment. It is one of several features considered, rather than a test that replaces investigation.

Prevalence within a breed also depends on inherited differences between family lines and on geographical area.

Typical symptoms

Itching shows in your dog's behaviour: licking, biting, scratching and rubbing. Commonly affected areas include the paws, face, ears, armpits and abdominal skin. However, signs are not distributed in the same way in every dog.

• Excessive licking or chewing of the paws.

• Rubbing the face and scratching other areas of skin.

• Red skin and thinning hair in scratched areas.

• Darkening and thickening of the skin as the disease becomes long-standing.

• Recurring ear problems or skin infections.

Saliva can stain hair on the paws or other licked areas brownish.

Early skin changes may include small red patches and bumps. Later, scaling, bloody crusts and scratch marks can develop. Some dogs rub their bottom along the floor because of itching.

Less common signs include allergic rhinitis and inflammation of the eye's conjunctiva, while skin signs are typical.

Complications and consequences

Scratching and licking can break the skin. Long-standing disease can involve hair loss, crusting, and thickened, darker skin. Secondary infection often increases signs and may temporarily make a previously effective treatment plan insufficient.

Atopy is lifelong, but treatment gives many dogs a good quality of life. Flare-ups can occur even during treatment, and a plan is needed to manage them.

Continuous itching causes prolonged stress. It can also lead to behavioural changes such as irritability. Staphylococcal bacteria and Malassezia yeast are common in secondary skin and ear infections.

Diagnosis at the vet

Atopy is diagnosed from the history of signs, skin examination and exclusion of other causes of itching. A single blood test cannot confirm it. The vet asks about age at onset, seasonality, previous treatments and their effects.

Other possible causes, such as fleas, parasitic mites and bacterial or yeast skin infections, are investigated or treated first. Additional signs caused by microorganisms can make it difficult to assess the underlying allergic signs.

Investigating food-related signs may require an elimination diet, a restricted diet trial planned by your vet. During the trial, the effect of diet on itching is assessed. Simply changing food brands or flavours at random is not equivalent to this planned investigation.

Allergen testing is used particularly when immunotherapy is being planned. Skin tests or blood antibody tests help select allergens relevant to your dog, but a positive result alone does not prove atopy. Results must fit the history: a finding that indicates exposure alone does not show which substance causes signs in everyday life.

Samples from the skin and ear canals are checked for parasites, bacteria and yeasts. Similar itching can also result from sarcoptic mange, flea allergy and contact allergy. If the signs are atypical, hormonal disease and skin tumours are also considered among the possible alternative diagnoses.

The vet may use the Favrot criteria, a list of features compatible with atopy, to support investigation. Examples include onset before 3 years of age, affected front paws and itching before visible skin changes. When 5 features are present, the criteria have about 85% sensitivity and about 79% specificity for distinguishing other dogs. The criteria are not applied to food-induced atopic dermatitis.

Treatment

The vet prescribes treatment based on your dog's signs, skin changes and previous response. The current itching and skin inflammation are brought under control first. Maintenance treatment is then needed to help prevent new flare-ups.

Itching and inflammation can be treated with medicines such as corticosteroids, JAK inhibitors or targeted antibody therapy. Medicines that modify the immune response may also be used for long-term control. Do not give your dog a human allergy medicine unless prescribed by a vet.

A fast-acting corticosteroid can help with a severe acute flare-up, but long-term use carries a risk of adverse effects.

Topical treatments support the skin and can remove allergens and treat confirmed microbial overgrowth. They may include washes, rinses or other skin products chosen by your vet.

Allergen-specific immunotherapy aims to change your dog's response to identified allergens. A response takes 3–12 months to develop. It is therefore unsuitable for rapidly treating an acute flare-up.

Immunotherapy can have adverse effects, most commonly increased itching. A severe systemic reaction is very rare but possible.

Secondary skin and ear infections are also treated separately. If control is difficult, assessment by a vet with expertise in skin disease may help.

In a study of 664 dogs, about 60% of those receiving injectable immunotherapy for at least 9 months had a reduction in itching of more than 50%. About half of the dogs that benefited still needed other medicines alongside it.

Ciclosporin's itch-relieving effect develops slowly, taking as long as 4–6 weeks. The most common adverse effects are vomiting, diarrhoea and loss of appetite. Antihistamines have little effect on an acute severe flare-up. Essential fatty acids can take 2 months to have an effect, so they are used to support other treatment.

Immunotherapy can be given by injections under the skin or by treatment placed under the tongue. Its effect is assessed by comparing signs and itching in the same seasons in different years. At least 12 months of treatment are needed for assessment, because the first few months do not yet show the final response.

Antibody therapy targeting the signalling substance IL-31 acts rapidly, so it can also be used to control acute itching. Its most common adverse effects are tiredness and digestive signs. Long-term use of a topical corticosteroid can, in turn, thin the skin.

Prevention

Atopy cannot be prevented completely, because susceptibility is inherited. The practical aim is to identify factors that worsen it and reduce exposure where possible. Not every pollen or other environmental substance can be avoided.

Vet-guided parasite control, support for the skin barrier and management of infections are part of preventing flare-ups. Follow the maintenance plan even during better periods if that is what has been agreed.

Atopic or allergic dogs should not be used for breeding. Once the disease is diagnosed, proactive topical care and maintenance medicines chosen for your dog's pattern of disease can also reduce flare-ups.

Important for dog owners

Choose a few things that are easy to track in a diary: the amount of itching, paw licking, ear signs and how well your dog sleeps at night. Record treatments, diet and dates. Take comparison photographs of visible skin areas in the same lighting. At rechecks, also explain how treatment has actually been carried out, so a lack of effect can be distinguished from practical difficulties.

Ask for two written plans: what to do during a stable phase and how to get in touch when a flare-up begins. Agree who changes medicines and when rechecks take place. If several people care for your dog, keep a shared treatment record. Explain the limits of your own daily routine too, so day-to-day care can be carried out consistently over the long term.

Frequently asked questions

Can a blood test diagnose atopy?

A blood test alone cannot confirm atopy. Diagnosis depends on the overall findings and investigation of other causes of itching. Allergen antibody testing can help plan immunotherapy, but results must be interpreted alongside signs and your dog's actual exposures.

Can atopic dermatitis in dogs be cured completely?

The disease is usually lifelong, but its signs can often be controlled well. Treatment may change with the seasons and your dog's circumstances. A good period without signs is a valuable result, but discuss stopping maintenance treatment separately with your vet.

Does all paw licking mean atopy?

No. Paws are commonly affected by atopy, but other skin diseases can cause similar itching. The vet investigates other possible causes and assesses your dog's full history before describing long-term care as treatment for atopy.

Does immunotherapy relieve itching immediately?

Immunotherapy acts slowly and does not replace rapid control of signs when that is needed. Its purpose is to change the response to relevant allergens over the long term. Some dogs need other medicines alongside it, and benefit is assessed at agreed rechecks.

Can atopy affect only the ears?

In a small proportion of dogs, recurring ear inflammation can be the only obvious clinical sign. That does not mean every recurring ear problem is atopy. The ears and other possible underlying causes need investigation so treatment targets the right problem.