Scratch That Itch!
Skin Allergies In Dogs
Allergic skin disease is a common problem in dogs and one that may be difficult to determine the cause of and frustrating to manage.
Signs of allergic skin disease in dogs include inflamed skin that is pinker/redder than normal, warmer than normal, and itchy. Affected dogs will scratch, lick, rub or chew themselves constantly.
You may notice your dog rubbing its face on the ground, chewing its paws, rubbing against fences or even rolling around on the ground to scratch that elusive itch. Excessive scratching results in trauma to the skin, so you may also notice hair loss and a red rash over affected areas.
Secondary bacterial or yeast infections of the skin may develop in chronic cases, so the coat may become greasy in appearance and have a nasty smell. Flakes of skin in the coat are also common.
Dogs can be allergic to numerous things including the bites of insects (e.g. fleas), environmental allergens (e.g. pollens, moulds, and house dust), contact with various plants or chemicals or even the food they are eating.
Flick the fleas
The most common skin allergy that affects dogs is flea bite allergy. Flea allergy dermatitis (FAD) typically results in a sparse, dry hair coat at the base of the tail with itchiness more severe in this area. Dogs with FAD only need one flea bite to start the allergic reaction so you may not notice that your dog has fleas.
Comb your dog, especially over the back and tail area, onto a dampened sheet of white paper. Black dots that turn red on contact with the moisture are actually flea faeces, which contain dried blood.
To ensure this is not part, or all, of the problem, it is necessary to use rigorous flea control. Use of a topical ‘spot-on’ formulation or monthly chew is recommended as these kill adult fleas on the dog within 12-24 hours with a residual action of up to a month, preventing further egg-laying, as well as killing flea larvae in the dog’s environment.
Products containing an Insect Growth Regulator (IGR) are also available that stop flea reproduction. If a more rapid flea kill is required, a flea spray or tablets available from your vet may be desirable. It is also important to treat any other dogs or cats in the household, plus wash any pet bedding, vacuum carpets, areas beneath furniture and even closets. In cases of severe allergy or massive flea infestations, flea bombing the house may be necessary and treating outdoor areas where your dog frequents with insecticides.
Alternatively, hire a professional pest controller, especially if you have areas underneath the house that are accessible to pets. Dense vegetation near the home should be mowed or clipped and leaf litter and debris removed to allow the soil to dry.
If the scratching persists then an allergy of a different type may be the problem, such as food allergies. Any food ingredient can cause an allergy although the protein is usually the offender. This is diagnosed by feeding a hypoallergenic diet for at least 8 weeks.
The goal is to feed a diet that contains protein and carbohydrate sources that your dog has never had before. Venison, rabbit, duck or kangaroo meats are often used as the protein source and rice or potato is often used as the carbohydrate source. This can be difficult to achieve consistently at home but your vet can prescribe a specialised diet. It is necessary to feed this as the sole diet (no treats, scraps, bones etc.) for at least 8 weeks to see what the response is.
Atopy is the second most common allergic skin disorder in dogs and is a genetically inherited disease. Atopic dogs are allergic to substances (allergens) in the environment that are inhaled or absorbed through the skin
House dust mites are the main offender leading to a non-seasonal dermatitis, although the severity of the signs may vary with changes in the environmental allergenic load. More rarely, pollen allergies (trees, weeds and grasses) are involved, which may typically lead to a seasonal dermatitis. Affected dogs are often extremely itchy (pruritic), especially around the face, belly, armpits, lower legs and feet. Scratching of the trunk, rubbing of the face (lips, chin, ears etc) and chewing of the feet are frequently seen. The intense itching can make them irritable and less tolerant of being handled.
It is estimated that around 10% of dogs suffer from atopic dermatitis and the first signs usually occur between 6 months and 3 years of age. Although it is seen in all breeds of dogs, including mixed-breed dogs, there is a greater than expected incidence in terriers, setters, Golden and Labrador retrievers, Dalmatians, English bulldogs and the Chinese Shar-Pei. The mode of inheritance is not known but is it is considered best not to breed affected dogs, their parents and preferably their siblings as well.
Atopy can be diagnosed by a blood or skin test. Determining which allergens are a problem for your dog can help you to avoid or at least reduce exposure to it. For example, dogs with an allergy to house dust mites may benefit from spending more time outside and/or in rooms with little house dust. If pollens are the problem, then keeping the dog inside when grasses and trees are flowering or removal of certain plants may be helpful in the management of the symptoms.
Atopic dermatitis cannot usually be cured, but it can be controlled to improve the dog’s quality of life. Treatment involves a combination of therapies and usually includes cortisone (which blocks the allergic reaction in most cases) and antihistamines.
Drugs specifically developed for the treatment of canine atopic dermatitis are also available. One contains cyclosporin – a natural product extracted from a fungus which acts as a selective immunomodulator – and is proven as effective as corticosteroids in reducing pruritus and skin lesions without the side-effects. Another drug contains oclacitinib, which targets specific immune factors to quickly break the itch cycle with reduced side-effects compared to other therapies. Antibiotics are also often required to treat secondary bacterial infections.
Medicated shampoos can be helpful, especially those that are soap or detergent-free and therefore do not strip the natural oils from the coat. There are soothing shampoos available containing oatmeal and aloe vera as well as leave-on conditioners that help reduce skin inflammation.
Immunotherapy is another important tool in combating allergies. After intradermal skin testing has been performed, a veterinary dermatologist can develop hyposensitisation vaccines to the allergen/s identified. These are especially indicated in severe, year-round cases or where dogs suffer undesirable side-effects to medical therapy.
Complementary therapies, including acupuncture, can also help alleviate allergy symptoms and reduce reliance on traditional medicines in some cases. Fatty acid supplementation can also be beneficial. Your veterinarian will recommend the best combination of therapies to manage your dog’s atopy.
Allergic contact dermatitis
Contact allergies, such as to certain plants, carpet cleaners and other chemicals, plastic etc. are quite rare in dogs and signs are usually restricted to contact areas where the hair is absent or thin. Differentiation between the different types of allergic skin diseases can be difficult and other itchy skin conditions, such as sarcoptic mange, skin infections, and drug hypersensitivities, also need to be ruled out.
Additionally, more than one skin complaint can be present at the same time, so if your dog is scratching like mad and driving you crazy, the best option is to head to your vet to get the problem ‘licked’. The sooner your vet can start investigating the cause, or refer you to a veterinary dermatologist if necessary, the sooner the appropriate treatment and advice on managing or preventing further problems can be given. More importantly, the sooner your dog will thank you.
Contributor: Dr Julia Adams BVSc