Now that spring has arrived we are starting to see more dogs with allergies, which are one of the most frustrating conditions that we treat as veterinarians. Skin allergies can be caused by many different substances or ‘allergens’ and include, flea bites, food, contact allergies (eg wandering dew), inhaled substances or even normal skin surface bacteria or yeast.
Atopic dermatitis (atopy) is an allergy to substances that are either inhaled into the lungs and then are absorbed into the body, or they are absorbed through the skin. The ‘allergen’ is usually to normal harmless substances eg. pollens (grass/trees/weeds) moulds, house dust mites. 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.
The first signs we generally see are licking, scratching or rubbing, with the skin often looking normal at this stage. Most dogs start developing signs around 1-3 years of age after initially being exposed for a season or two to the allergen. 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 (a darkening of the skin). The skin may also become malodorous with an increase in bacteria/yeast on the coat which may worsen the itching. Saliva from constant licking also leads to a rust brown discolouration of the hairs. Areas affected with atopic dermatitis are usually the paws, face, ears, underarms, groin and front legs. The signs are generally seasonal (often spring/summer), especially if the allergy is to pollens which can be worse in temperate environments with long allergy seasons and high pollen counts eg Hawkes Bay. Dogs may also have concurrent allergies to fleas and some foods which can increase the severity of the signs.
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, or breed of dog (some very prone to atopy). Your vet will also visually check for evidence of fleas. One other 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 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(s). This is performed by a dermatology specialist and usually requires a referral from your vet. Last but not least, trial therapy to rule out other allergies may be elicited by monitoring response after removing possible allergens, eg flea control; changing to a low allergen diet (please consult your vet) for at least 6-8 weeks – food allergies generally only make up 10% of allergies but it’s worth ruling out; changing bedding; and avoiding grass.
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 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 or sprays especially if the area is small (and inaccessible to the tongue!), cortisone (steroids) or Apoquel a drug that blocks the action of the itch nerve – effectively stopping the scratching but without the associated side effects of cortisone use.
Ongoing management can include:
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 lead to unnecessary suffering.
Please make an appointment with your vet if you are concerned about your pets' skin.