Stop the itching: What you need to know about allergies in dogs

What is an allergic reaction?

An allergic reaction is the result of ongoing exposure to an allergenic substance. The immune cells in the body build up a memory of the allergen. The more contact the animal makes with the allergen, the more the body reacts by releasing histamine and other inflammatory mediators. This looks like an dog that is scratching constantly for no apparent reason because the itchy feeling precedes lesions on the skin which come from self-trauma from scratching or infection from relentless scratching.

What are the symptoms?

Atopic dermatitis usually looks like itchy skin, so the most common signs are scratching and chewing of the armpits, between the hind legs and abdomen, the face and the ears. Affected dogs will often lick, or even chew, their feet.

You will observe redness in the affected areas, and the dog’s continual licking and scratching at the site only makes it further inflamed. This can lead to secondary fungal or bacterial infections on the skin and the ears. Check your dog’s ears by pulling back the ear flap and looking for redness and discharge.

Typically these symptoms start between 1 and 3 years of age, however onset can occur from as early as 4 months to as late as 7 years of age.

Some of the common allergenic plants are Wandering Jew, Ragweed, Sorrel, Dock, Clover, Kikuyu, Papsalum, Fescue, Privet, Pine Oak, Birch and Couch grass. The only way to tell which of these your dog is allergic to is to perform allergy testing at the vet.

Expert advice from Dr Felicia:

A common giveaway on physical examination for potential ongoing allergic itch especially for lighter coloured dogs is the presence of saliva staining on the feet. Over time the feet will be stained a brown colour from ongoing licking.

How can atopic dermatitis be treated?

Like many allergies, Atopic Dermatitis is a life-long condition that can’t be cured, however it can be managed in a few different ways:

• Anti-itch medications include corticosteroids or other more targeted skin anti-inflammatory medications which can be given as a daily tablet or as a monthly injection. For milder cases some patients can be managed on anti-histamines. These medications help to dampen the immune response to the allergen, resulting in less itch.
• Medications to treat/manage secondary infections, usually oral antibiotics or antifungals (to treat more generalised secondary infections) though some patients can be managed with medicated shampoos, conditioners and skin lotions or creams. Before using medication, always consult your vet for advice on what to use and how to use it, and be mindful of any potential side effects.
• While this isn’t often possible when it comes to environmental allergens, try to remove the source of the allergy as much as you can. Unfortunately, pollens can be carried up to 80km in the air, and dust mites are everywhere.

• If you can’t avoid the allergen, wipe or wash your dog’s paws to remove allergens after walks and hikes. In addition to this, you can remove the allergenic weeds from your backyard. Regular washing with a gentle shampoo can reduce the allergenic load on your pet’s skin.
• Hyposensitisation therapy (allergy “vaccine” shots) is the administration of a series of injections by which your dog will gradually become desensitised to the targeted allergens. The effectiveness of this treatment can vary; however, in 75% of pets some relief has been recognised.
• Supplements such as biotin and omega-3 oils have a natural anti-inflammatory effect and support coat health, improving barrier function. These can be given as supplements or are part of specially formulated diets that support dogs with itchy skin.

Expert advice from Dr Felicia:

Diagnosis of atopic dermatitis in dogs is a diagnosis of exclusion which means that other diseases causing itchy skin should be eliminated first. This usually involves parasite prevention and dietary trial, and from there testing for allergies can be considered if immunotherapy is desired. Many patients may not proceed with allergy testing particularly if symptoms can be managed medically or with supportive care.

Flea allergy dermatitis

What is it?

Flea allergy dermatitis (FAD) is also called “flea bite hypersensitivity” and is an allergic reaction to flea saliva. Not many fleas are needed to cause a dog to experience intense itching. It is one of the most common causes of itchiness in dogs.

In rare cases, dogs have been found to be allergic to other insects such as mosquitos and midges.

What are the symptoms?

Dogs that are allergic to fleas will chew and bite their backs, back legs, bellies or tails – sometimes even until it bleeds! The skin often becomes red, raw and painful and you may even see little flecks of flea dirt (which is flea poo) or fleas themselves walking through the haircoat near the skin.

Flea bites often lead to hot spots – red, inflamed and/or infected lesions on the skin –  due to the trauma from dogs chewing themselves in trying relieve their intense itching.

Expert advice from Dr Felicia:

The most common location for intense itch due to flea allergy is around the neck and shoulders, and around the tail base. This distribution as well as the presence of ‘flea dirt’ on the coat provide helpful clues that flea allergy is responsible for the itch. It is now seen more rarely than before due to the widespread use of effective parasite prevention.

The most effective method is to be very diligent and use products to kill and prevent fleas from infesting your dog. As fleas are pretty much everywhere, it is almost impossible for your dog not to have fleas unless you are using a good-quality flea control product all year around.

There are many efficient and convenient products available, but it’s always advisable to ask your vet for advice. Your vet may prescribe steroids and antihistamines to break the cycle of itching and scratching. Regular warm baths with medicated anti-itch shampoo and conditioner can also help.

You should also vacuum regularly and wash your pet’s bedding frequently in hot water (>60 degrees Celsius).

Be aware of possible flea exposures if you have other dogs visiting (especially if you don’t know whether they are on flea control or not) or if your dog visits places where there are other dogs, such as dog boarding, doggy daycare and dog parks.

Flea prevention all year round is really important, and even more so if your dog has FAD. Once you have a flea infestation on your dog and in your home, it becomes a nightmare and is very difficult to resolve. Make sure all other pets in the household are also treated.

Using a flea comb may help to find out if your dog has fleas, however, fleas are tricky to find as they are good at hiding and running away to escaping the comb. Also, only 5% of fleas actually live on the dog; the remaining 95% ( including the eggs, larvae and pupae) live in the environment (e.g. bedding, parks, carpets, gaps in floorboards and garden). Learn more about how to control fleas.