Dr Primrose Moss – Freelance Veterinary Writer

In Part 1, we covered the causes of allergies, including food and environmental allergens, and how we can recognise allergic skin disease. But if your dog has chronically itchy, uncomfortable skin you’re probably wondering, “What can we do to help them?”. In Part 2, we’ll look at how we manage allergic skin disease, including what you can do to help at home and the treatments that vets can provide.

1.   Ruling out other conditions

Allergic skin disease is a chronic condition but can often wax and wane, with flareups caused by a spike in allergens like pollen or other irritants like secondary infection or parasites. As a result, we commonly see owners initially bring in their itchy dogs for a specific skin or ear infection rather than their chronic, lower-level symptoms. 

When we see an itchy dog, we therefore look for signs of infection or parasites first. This is important, as the treatments for allergies may dampen the immune response and allow any infection or parasite infestation that is present to worsen. Ruling out parasites and infections often involves assessing the ears with an otoscope, performing skin scrapes or ear cytology to look for bacteria, yeast and mites under the microscope, and/or treating the dog with anti-parasite treatments.

While skin infections and parasites can mimic allergic skin disease, it’s very common for dogs with allergic skin disease to develop infections as secondary issues, especially in the ears. This is because allergic skin disease is associated with excessive licking and chewing, a disrupted skin barrier, and inflammation and mild swelling which in the ears create a warmer, moister environment. 

Frequently, the chronic symptoms of allergic skin disease are mild enough that owners don’t see them as a problem; instead, we see dogs being brought back in several times a year with ear or skin infections (otitis and pyoderma, respectively), which cause significant pain and, especially in the case of ear infections, become progressively harder to treat and manage throughout their life. At least initially, these acute infections often respond rapidly to ear drops and owners, understandably, think the safest (and cheapest!) option is to simply manage these acute infections as they arise. However, this isn’t always the case. 

When dogs have recurrent, painful ear infections they often become too distressed for ear cleaning to be performed or ear drops to be properly applied. With repeated infections, thickening and scar tissue begins to change the normal anatomy of the ear canal and predisposes the dog to more frequent and severe infections; in some cases, this results in surgery being required to remove the entire ear canal as the infections have become too severe to manage. If your dog is experiencing recurrent ear or skin infections, I’d encourage you to discuss the possibility of allergies with your vet and consider longer-term management. 

Treatment of parasites is usually relatively straightforward, involving a course of anti-parasite treatment. Skin infections frequently require antibiotics, although milder infections may be managed with topical antibiotic ointments or shampooing, often with chlorhexidine disinfectant. Ear infections can be some of the trickiest to manage; these often respond to antibiotic and antifungal ear drops but may require additional cleaning. This can be at home, often with a gentle cleaner like Otodine. In severe cases cleaning under sedation or general anaesthetic may be required. If an infection is severe or isn’t responding, a swab may need to be taken for culture and sensitivity, to identify the best antibiotic to use.

Once any infections or parasites are controlled – what next? Often, this is the stage at which owners don’t return. By this point, I doubt your dog is keen to revisit the vets, and if their symptoms seem to have resolved and they’re back to their happy selves, you might be tempted to leave things until they flare up again. But if your dog does have underlying allergies and is having regular flare ups, this is the time to begin longer-term management. By managing the chronic itchiness and inflammation, you can reduce the frequency of flare ups and avoid permanent changes occurring.

2.   Reducing – or eliminating – exposure to allergens

While there are many treatments that can help allergic dogs, the simplest – and arguably best – would be to eliminate their exposure to allergens. This usually isn’t feasible – we can’t avoid pollen completely, as much as those of us with hay fever might wish we could! However, reducing allergen exposure is an important part of treating allergic skin disease.

So, what can you do? First, although food allergies are less common than environmental ones, it’s worthwhile carrying out a thorough food trial with your allergic dog. The aim is to eliminate any potentially allergenic proteins from their diet for a full 6-8 weeks. It’s important to pick the right diet – I usually recommend Royal Canin anallergenic or hypoallergenic (anallergenic is the ‘best’ but is a little less palatable), Purina hypoallergenic or Hill’s z/d. Unfortunately, the term hypoallergenic isn’t regulated, so many high street diets with this label aren’t strict enough to give good results. You may also hear of novel protein diets – in an ideal world, a diet trial would be based on a protein that your dog has never previously been exposed to. However, in practice it’s almost impossible to find a diet that exclusively contains proteins our dogs today have never been exposed to – which is why a hypoallergenic diet is typically recommended.

It’s important to note that if your dog does sneak any titbits, treats or scavenging during the food trial, this can flare things up again and mean that you need to restart it.

Towards the end of the food trial, if things have improved, we usually recommend weaning off any allergy medication and then re-challenging with their normal foods to see if this causes a flare-up. This is the best way to confirm a dietary allergy – and if diet is partially or entirely responsible for your dog’s allergies, it’s worthwhile considering a long-term hypoallergenic diet. 

If your dog’s allergies are environmental rather than food related, there are still a few things you can do. First, even simply rinsing their paws and belly after walks with plain water (or a gentle oatmeal-based shampoo) can make a big difference, removing some of the allergens before they have a chance to cause inflammation. Many dogs are also allergic to things like dust mites, so ensuring their bedding and areas they occupy are as dust free and clean as possible may help – though using too many strong cleaning products may do more harm than good.

For dogs with ear inflammation related to their allergies, regular ear cleaning can also help. This can be a water based, gentle cleanser (like Otodine), which can be used a few times a week. Alternatively, if your dog is susceptible to bacterial infections your vet may recommend a cleaner with a disinfectant like chlorhexidine for longer term use, or an oilier cleaner containing ingredients like squalene if your dog is more prone to excessive wax production and yeast infections. It’s best to discuss with your vet what’s likely to work best for your dog – especially as some of these cleaners aren’t ideal if there’s an active infection. Cleaning 1-2 times a week is often sufficient to keep the ears clean and clear, flushing out excess debris and pollens and reducing the likelihood of infection.

3.   Improving the health of the skin barrier

Dogs with allergic skin disease are known to have a poorer skin barrier – and it’s this barrier that’s critical for keeping allergens and infections out and moisture in. So what can we do to help support our dogs’ skin barriers?

Bathing can be helpful not just to remove environmental allergens but also to help the skin barrier. Oatmeal based shampoos or even just plain oatmeal baths can help to soothe the skin. I usually recommend bathing once daily for 3-5 days with an oatmeal-based shampoo like Allermyl, lathering the coat and leaving it on for 10 minutes each time before rinsing. This can then be tapered down to every other day and eventually once a week long term. If your dog has other skin issues like greasy skin or an infection, your vet may recommend other shampoos which contain disinfectant or are designed to remove grease, but these can be too drying for a lot of allergic dogs long term. 

After bathing, it’s important to use a dog-specific conditioning treatment to prevent water loss and dry skin. Again, there are a range of suitable products available, with Ermidra spray being one example.

Supplementation with fatty acids is one further way we can try to support dogs’ skin barriers. There is some evidence that, at least in earlier or milder cases of allergic skin disease, supplementation with essential fatty acids like Omega 3 can help to reduce itching¹. Various products are available, and it’s important to choose a dog safe one like Yuderm as human products can be unsuitable.

4.   Medications

Allergic skin disease in dogs is the topic of much research due to its prevalence and the extent to which it can affect dogs’ lives. As a result, there are a number of different treatment options available. These treatments typically follow a pattern – the stronger (and more effective) they are, generally the more side effects they cause.

Steroids (like prednisolone) are a mainstay of treatment for many cases of allergic skin disease. They’ve been around for a long time – and they’re very effective. Oral steroids can rapidly damp down inflammation during acute flare-ups and they are a long term option for some patients. Importantly, they’re a lot cheaper than some of the newer medications that are available. However, steroids have a range of side effects. In the short term, they usually cause increased appetite, thirst and urination and in some dogs can alter behaviour. Longer term, they can cause weight gain, skin changes including thinning skin and poorer coat, increased infections and poorer wound healing, muscle wastage, diabetes and more. If your dog is on long term steroids, it’s important to work with your vet to taper them down to the lowest effective dose to minimise these effects. 

One way of minimising the systemic effects of steroids is to apply them topically. While a small amount is absorbed, the systemic dose is significantly lower than using oral medication. Steroid sprays for the paws and ear drops can be useful in some patients if the inflammation is relatively localised.

Because of the side effects associated with steroids, a range of other medications have been used to manage allergic skin disease. One of these is ciclosporin (Atopica), which like steroids acts as an anti-inflammatory at lower doses and an immunosuppressive at high doses. Again, it’s associated with a range of side effects, but can be better tolerated than steroids. It’s relatively rarely used nowadays due to the other medications available.

More commonly, vets will recommend trialling a medication like lokivetmab (Cytopoint) or oclacitinib (Apoquel) for long term use. But how do these work? These newer generation drugs are a little different to the anti-inflammatory / immunosuppressive medications used previously.

Cytopoint is a monthly injection consisting of antibodies to a specific inflammatory molecule, IL-31, which has been identified as a critical part of the ‘itch’ pathway. It’s injected like a vaccine under the skin and side effects are rare. While symptoms usually begin to improve rapidly, within a few days, it can take 2 doses for the full effect to be seen.

Apoquel is an oral tablet, usually taken daily with an initial 2 week period of twice daily dosing. It’s an inhibitor of a specific enzyme in the itching pathway, so like cytopoint is a lot more targeted than steroids with fewer side effects. It usually takes effect rapidly, within 24 hours, and can be used alone or alongside medications like Cytopoint. Side effects from Apoquel are rare but may include changes in blood cell counts so regular (usually yearly) blood tests are recommended during treatment. There is also some limited evidence that Apoquel may slightly increase the risk of infections and cancer due to its effects on the immune system; however, this minimal risk is often greatly outweighed by the huge improvement in quality of life seen in many dogs.

You may be wondering, if Apoquel and Cytopoint are so similar, how do we choose between them? The answer is that it depends on which a specific dog will tolerate best, and how well they seem to respond – although they typically have similar efficacy², occasionally a dog does well with one and not the other. Age is also a factor; Cytopoint is safe to use at any age whereas Apoquel is only licensed for dogs over 12 months of age. While the two can be safely given together, this doesn’t generally improve symptoms more than using one alone.

You may be wondering where antihistamines are in this list – after all, they’re one of the most commonly used medications for allergies in humans. Antihistamines like chlorphenamine can be used in dogs, but there’s very limited evidence for their effects on allergic skin disease. For most dogs, however, side effects are generally limited to sleepiness – so it may be worth discussing with your vet whether it’s worth trying antihistamines, usually alongside other treatment.

5.   Immunotherapy

Immunotherapy stands alone as a very different type of treatment for environmental allergies (unfortunately it doesn’t treat food allergies). Unlike traditional medication, the aim of immunotherapy is to gradually desensitise the immune system. The end goal is for the immune system to tolerate the allergens to which it has previously reacted inappropriately. 

It’s reportedly one of the most successful options to treat allergic skin disease – and it can be life changing for some dogs, potentially eliminating the need for other medications. However, it’s important to note that immunotherapy can be expensive and not all dogs will respond well – an anecdotal rule of thumb is that around a third of dogs experience a large improvement in their symptoms, one third a small improvement, and one third no change. Improvement may also take some time – it may take up to a year to see a significant difference – and treatment will usually need to continue for life.

So how does it work? Once environmental allergies have been diagnosed, the next step is to identify allergens that correspond to high levels of antibody in a dog’s blood. If high levels of antibody are present against an allergen, it’s more likely this is one of the allergens causing skin problems. Two methods exist to identify these allergens: intradermal skin testing (IDST) and a blood test. IDST is a more involved process whereby numerous small areas of skin are exposed to various different allergens; it is sometimes used, especially at referral centres, but blood tests are more common and simpler. Before testing, you may need to stop giving medications like steroids as these could affect the results. Blood samples are analysed by a laboratory, and the results can then be used to order immunotherapy based on the most likely allergens. 

The immunotherapy treatment itself consists of injections given subcutaneously (under the skin), like a vaccine. How frequently a dog requires these injections depends on the individual case – various dosing protocols exist – but often starts off more frequently before tapering down. Importantly, the process is staged, with a lower ‘dose’ of allergen given initially, gradually increasing to a higher dose over time.

You may occasionally see adverts for fur or saliva tests that guarantee they will identify a dog’s allergens (I know I get them!) – but sadly these results are generally meaningless. Some owners report good results after avoiding a reported allergen, but this is almost certainly coincidence as some allergens are rather common and the reports frequently list a vast array of possible triggers. If you’re tempted by one of these tests, it’s worth discussing it with your vet first.

Conclusion

Allergic skin disease may not be curable, but it can be managed, increasingly effectively as further research is carried out and medications developed. As a dog owner, it can be hard to fully understand the options available for managing this tricky condition – and more often than not, it takes trial and error and a combination of home care and treatments to manage it effectively. While this article attempts to shed some light, it’s worth discussing your dog’s specific case with your vet; combining your vet’s knowledge of allergies with your own knowledge of your dog’s unique case is the best way to keep them as healthy and happy as possible.

References

1 – Bensignor, E., Morgan, D. M., & Nuttall, T. (2008). Efficacy of an essential fatty acid-enriched diet in managing canine atopic dermatitis: a randomized, single-blinded, cross-over study. Veterinary dermatology, 19(3), 156–162. https://doi.org/10.1111/j.1365-3164.2008.00670.x
2 – Lee S, Yun T, Koo Y, Chae Y, Lee D, Choi D, Choi Y, Kim H, Yang M, Kang B.  Clinical Efficacy of Oclacitinib and Lokivetmab in Dogs with Canine Atopic Dermatitis.  J Vet Clin 2021;38:127-134.  https://doi.org/10.17555/jvc.2021.38.3.127