Hmmm…This is a good question! It’s one as vets, that we often receive from clients. While antihistamines are effective for humans to treat allergies, do they work for dogs in the same way? Unsurprisingly, the answer isn’t straightforward.

Firstly, it’s not that they won’t work, it’s more a case of how well they will work for your dog and whether their use has any significant impact upon the level of your dog’s pruritis (“itchiness”). Frequently, anti-histamines may not offer sufficient control of symptoms. This may lead to a perpetual cycle of itchy “atopic” symptoms for your dog and frustration and despair on the owner’s behalf.

What exactly is an allergy then?

As previously discussed in former blogs, skin allergies (atopy) are the most common form of skin complaints we see in our canine patients in the UK. Up to 10% of dogs may be affected. A combination of genetic susceptibility and exposure to certain environmental (or sometimes dietary) allergens, may cause our dogs to rub, scratch, nibble, lick and bite themselves, in an attempt to resolve that pesky itch! Skin becomes red, inflamed and sore and secondary bacterial and yeast infections are common. Ear disease may also manifest, particularly in larger breed dogs.

The associated discomfort and feeling of irritability and “itch” can be enough to drive some animals crazy. It may be relentless for some severely affected animals. Allergens stimulate an inappropriate and exaggerated immune response within the dog’s body and a mixture of chemicals are released as a result. These chemicals include histamine…

And so how do anti-histamines work?

Given that histamine is one of the main chemicals involved in allergies, it seems logical to assume that an anti-histamine drug may alleviate symptoms. Alongside medicated shampoos and the use of high quality and (ideally) ethically sourced omega 3 essential fatty acids (such as those found in fish oils), anti-histamines may provide some relief to the cohort of dogs with very mild atopic disease.

However, it is important to realise that atopy unfortunately, is an ever-present disease. And whilst it may start seasonally at certain times of the year, over the course of a patient’s lifetime, it typically both worsens in terms of severity and additionally, becomes non-seasonal. Dogs may, therefore, show symptoms throughout the year. Relapses and frequent bouts of disease episodes or “flare-ups” are not uncommon. 

And which anti-histamine might help my dog?

Another tricky question… There are a number of anti-histamine drug options available and unfortunately, it can be impossible to know which precise one may help your individual dog. A realistic expectation might be to have to trial a number of drugs, each for a 2-3 week period, whilst keeping a diary of effectiveness. With hindsight, it may be noted that one particular anti-histamine medication, exceeds the others, and is superior in helping to relieve symptoms.

So what are the other treatment options?

When treating atopy, it often first helps to start by having an appreciation of what the significant allergies for the individual dog are. This may be achieved with either intradermal skin tests performed by a dermatologist, or through blood tests looking at antibody levels in your dog’s bloodstream. Whilst not necessarily able to document or pinpoint every cause of allergy in every dog, these tests are helpful in that they may help guide and plan management strategies and treatment. They may also allow a discussion to be started as to the best control strategies for allergen avoidance or reduction, and to minimise exposure for the dog in the first instance. 

As an example, house dust mites, often implicated in allergy, thrive in damp, humid and poorly ventilated environments. Improving ventilation, reducing humidity and preventing your pet from accessing soft furnishings/carpets, are all measures that will help reduce exposure to dust mites.  

Food intolerances may be suggested by blood tests too. However, for absolute clarification an 8-12 week exclusion food trial (and subsequent challenge with the dog’s original food), are necessary.

And specific drugs?

For moderate to severe allergies, a number of licensed treatment options exist. These may include (but are not limited to) tailored immunotherapy or the use of immunosuppressive medications (oclacitinib “apoquel” and cyclosporin “sporimmune”) amongst others. Steroids (and their many associated side effects), whilst used in the past, can essentially be avoided now, certainly long-term in most dogs, given the range of other treatment options we have available to us.

Immunotherapy involves having a solution specially manufactured, containing the precise allergens that your dog is allergic to. Increasing amount of this solution are regularly injected into your dog, the aim being to eventually “desensitise” their immune systems. After an initial more intense induction phase, ongoing monthly injections are the norm with success reported in around 80-85% of cases if treated early enough within the dog’s lifetime.

A relatively new, safe novel treatment to the market is “cytopoint.” Rather than acting as a traditional drug, this biological medicine works like your dog’s own immune system, blocking the protein that sends itch signals to your dog’s brain. As an injection, monthly administration will effectively keep most dogs’ atopy under control. 

Cost versus reward in treatment options

Whilst any of these treatments are undeniably more expensive than over the counter anti-histamines, they are likely to offer vastly superior, safe and effective effects. This will hugely benefit your dog in terms of comfort and wellbeing. 

It is also important to remember that for any treatment to be successful, attention, as ever with atopic dogs, must also be paid to regular ectoparasite control, along with the control of bacterial and yeast infections, where they exist.

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