Skin allergies in dogs

Content by Dr Siân Burwood MA VetMB MRCVS

Skin allergies are where an overactive immune system in your dog causes release of chemicals that makes their skin itchy. As your dog scratches, rubs and licks the affected skin, further substances are released causing a vicious cycle of itching, pain and damage to the skin. 

Secondary infections are more likely in the damaged skin, and in the long term the skin becomes scarred and thickened.

Skin allergies are seen increasingly commonly in dogs. While not fatal, they can cause real suffering for both dogs and their owners.

• Skin allergies are a very common problem in modern dogs and can cause a lot of distress
• Any breed may be affected, but certain ones such as Bulldogs, Bull Terriers and West Highland White Terriers are especially prone
• There are many possible allergens, and it can be hard to work out exactly what causes the problem
• Working together with your vet to find a consistent management plan is essential, but can lead to good quality of life for dogs with this lifelong condition

Skin allergies happen when the body detects an allergen – something that the immune system does not recognise as itself – but then has an overreaction to it.

Every dog has an ‘itch threshold’ above which they start to itch. For allergic dogs this is really low, so levels of allergens that wouldn’t affect a normal dog can cause serious problems. Not every allergic dog is allergic to the same thing (or things), or to the same degree.

Allergens are typically:

Food

Proteins – especially chicken, lamb, beef, pork and dairy – are usually the culprit in food allergies. Gluten and grains are often blamed by dog owners, but are very rarely the cause of problems.

Pollens, grasses, trees and weeds

Dogs don’t experience hay fever in the same way humans do. But flowering of certain trees, bushes and grasses can release pollen allergens.

Household allergens

Every home, no matter how clean, is full of house dust mites. And along with various food storage mites, these can all be causes of allergy for our dogs. Sensitive dogs are also more likely to react to harsh or strong-smelling cleaning products (like Shake n’ Vac), candles and diffusers.

Auto-immune disease

Some dogs suffer from atopic dermatitis or atopy. This describes where the immune system itself doesn’t work properly, rather than just being allergic to a specific thing. These cases are almost impossible to distinguish, however, because these dogs react to pretty much everything.

Although any dog can be affected by allergic skin disease, genetics play a very important role. We know that certain breeds and lines are more affected than others. These include:

• West Highland White Terriers
• English Bull Terriers
• English Bulldogs/Old Tyme Bulldogs
• French Bulldogs
• Shar Peis
• Pugs
• Staffordshire Bull Terriers

Affected dogs should never be bred from, as they’re likely to produce affected puppies.

Mild skin allergies often present as dogs who will lick their paws more than you might expect and seem to be obsessed with foot washing. They may also use their paws to rub their face, and might rub their body against the furniture or roll around on their backs.

Their skin may always seem a little bit pink, and you might see patches of reddy-brown saliva staining on their fur – especially if it’s white!

For some dogs, the only sign of allergic skin disease you might see is recurrent ear infections.

Diagnosis

In milder cases, history and signs are often enough to make you and your vet suspicious of allergies. You may already have realised that they seem more itchy after certain foods, for example. Swabs of any ear or skin infections may be needed to see what secondary bacteria are involved.

Your vet is also likely to advise some common-sense options to help them logically rule out the most likely causes, including:

• Veterinary parasite treatment to make sure it’s not just fleas or mange
• Making sure you are feeding a good-quality consistent diet that avoids the most common allergens

Diagnosis and treatment of skin allergies must be logical and done as a team with your vet. It’s tempting to try all sorts of home and over-the-counter remedies first, but it can end up just being more confusing!

Treatment will involve:

• Regular veterinary parasite treatment
• Treatment of any secondary skin or ear infections
• A diet trial: 8-12 weeks of a well controlled hypoallergenic diet
• Essential fatty acid supplements
• Wiping down the skin after walks, and use of vet-approved shampoos as needed

Sometimes medications are needed in the short term to break the itch-scratch cycle.

Prognosis

Allergies can never be cured, but can be managed. In mild to moderate cases, once inflammation and itch is under control, use the treatments listed above and work together with your vet. Then your dog should be able to lead a happy life – either off or with only occasional medication.

Severe skin allergies can cause really distressing symptoms, and often from a young age. Affected dogs seem to be itchy more often than they are not, and often will not rest or sleep so they can scratch.

Their skin becomes very red, sometimes dry or sometimes greasy, with a strong musty smell. It may become flaky, or develop sticky oozy discharges as infections develop. Fur becomes thin and patchy in the places where the dog nibbles – especially over tops of the feet and base of the tail. They often have severe ear infections with lots of discharge and pain.

If these symptoms aren’t treated to get under control quickly, or if they are left to grumble for a long time, then secondary skin changes happen that cannot be reversed. Skin becomes thickened and leathery, often very dry, with darkened pigment. Fur may never grow back. Many aggressive dogs seen in practice are actually just suffering dogs with sore skin.

Diagnosis

In more severe cases, in addition to history and symptoms, identifying exactly what the allergy is to can be helpful. Your vet may recommend blood tests to look for antibody levels against certain allergens. These tests may not always be accurate (exposure versus allergy can be hard to distinguish) and are not exhaustive.

Your vet may also want to refer you to a dermatologist in extreme cases.

Treatment of severe skin allergies involves everything listed for more mild allergies (see above), but is also likely to involve more medication. Medications used to treat skin allergies include:

• JAK inhibitors (such as Apoquel, Zenrelia and Skylocalm) which block the ‘itch cascade’ of substances released from skin cells
• Antibody injections (such as Cytopoint) which mimic the body’s own immune system to block the itch cascade
• Steroids, which tone down the body’s immune response and are powerful anti-inflammatories
• Immunosuppressant drugs (like Atopica or Cyclavance) which block the immune system response
• Immunotherapy is where a vaccination is specially made for your individual dog against the allergen they’re allergic to

Steroids are usually the cheapest option, but are associated with a range of side effects. The other options have fewer side effects, but are more expensive. Your dog may need more than one of these drugs at different times, or need more as the years go by.

It is very useful for severely allergic dogs to be fed a ‘hydrolysed’ diet – a prescription diet where the proteins within it are treated in such a way that the body cannot recognise them to then overact to them. They need to be fed this and absolutely nothing else for it to work.

Prognosis

Allergies can never be cured, but by working together with your vet and being consistent about management, dogs can have a good quality of life of normal length.

When management is inconsistent and advice not followed, you’ll be at the vets more often. This means dealing with larger bills, as your vet has to get on top of all the secondary issues before they can start treating the underlying problem.

“I spend the majority of my life in general practice dealing with skin allergies in varying degrees of seriousness, and it can be a real welfare problem when not dealt with properly.

“I’d really encourage all caregivers to work as a team with their vet, because when this happens, you can get a happy dog who only needs to see you every 6 months or so. I have seen some of the most extreme cases, who need lots of medication, still be a perfectly happy dog with a lovely coat, because their owners are dedicated and consistent.

“The tricky cases are the ones where owners don’t return for rechecks because they feel the dog is better, but are then annoyed when it comes back. I have to go back to square one for these, treating the infections and the basics before I can even get to sorting ongoing management.”

Dr Siân Burwood, MA VetMB MRCVS

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