Itchy Skin in Dogs

Skin allergies in dogs are one of the most frustrating conditions that as veterinarians we treat.   Skin allergies can be caused by many different substances or ‘allergens’ and include, flea bites, food, contact allergies (eg wandering dew), inhaled substances (eg pollens, house dust mites, moulds) or even normal skin surface bacteria or yeast.  It is generally owing to a genetic predisposition in certain dogs, where repeated exposure of the allergen leads to an overreaction by the immune system to lead to the symptoms of skin allergy.   Unfortunately the condition is generally life-long with no cure, but often can be managed with time and patience.

Symptoms

The first signs we generally see are licking, scratching or rubbing with the skin often looking normal at this stage.  Dogs unfortunately don’t have the will power we generally have, and often scratch/lick and bite until the skin starts to become traumatised.  This leads to red, bumpy, or thickened skin eventually leading to hair loss and an increase in pigmentation. The skin may also become malodorous with an increase in bacteria/yeast on the coat which may worsen the itching.  Areas affected depend on the allergen, but are often the back/tail area with flea allergies,  feet/ears/underbelly/armpits with inhaled allergens or feet/hairless part of underbelly with contact allergy. 

Diagnosis

As you can imagine it would be pretty miserable feeling continually itchy and uncomfortable, so it’s vital you seek veterinary intervention before the skin becomes too damaged from self trauma.  Diagnosis of the condition may be aided by areas affected, age of onset, breed of dog (some very prone to skin allergies) or evidence of fleas.  One important condition to rule out is mites, so your vet may take a skin scraping to check and also check for bacteria or yeast on the skin surface.  Biopsies of the skin may be undertaken, which can rule out other diseases and point towards allergies, however it will not tell us what they are allergic to!  Blood testing (looking for antibodies against allergens) or better still skin allergy testing, by injecting small amounts of the allergen into the skin and looking for reactions, is a great way to try to determine the  offending substance – however this is expensive and requires consultation with a specialist dermatologist.  Lastly but not least, trial therapy may be elicited by monitoring response after removing possible allergens, eg flea control, changing to a low allergen diet.  

Treatment

Allergies can be very hard to treat and no one therapy is effective for them all.  However, in many dogs symptoms can be controlled with a variety of therapies. Often with most dogs, we need to break the itch scratch cycle first before starting on any specific therapy.  This may include antibiotics or anti-fungals to treat secondary bugs on the skin, soothing shampoos containing aloe-vera or colloidal oatmeal, topical creams especially if the area is small (and inaccessible to the tongue!), or cortisone.  Antihistamines are less effective in dogs compared with humans but can help prevent signs in some dogs.  Essential fatty acids can also decrease skin inflammation by up to 20%, but the correct ones need to be given, either by a supplement or in a special diet.  Atopica is a more recent treatment with minimum side effects compared with cortisone but is often cost prohibitive.   In some cases several allergens can add together to cause an animal to itch, where each individual substance alone would not be enough to cause an itching sensation – all animals should therefore be flea treated as sometimes this alone is enough, even if not suspected to be the cause.  Food trials may be started using a novel protein source the dog is not usually exposed to.  There are many specialist diets available, but they must be given exclusively at for at least 6-8 weeks to see if effective.  Although food allergies only make up 10% of all allergies, I still think this worth while as this can be an easy allergy to manage.  Washing feet after walks, and avoiding cut grass/high grass paddocks may help with contact allergies, or sometimes changing bedding to rule out wool allergy may be effective.  Desensitisation vaccines can be formulated on the basis of the skin or blood test containing the substance they are allergic to.  By continually exposing the dog to the offending substance the immune system may learn to stop overreacting.  This vaccination generally has to be given lifelong and is effective in improving clinical signs in 60-80% dogs – but is expensive.

Overall the take home message is remember allergies cannot be cured and there is no easy fix solution.  Finding effective therapies and working out the allergic substance(s) can be difficult and time consuming – patience is required!  However left untreated, allergic skin conditions, can be very distressing for your beloved pet and leads to unnecessary suffering.