Why is my dog scratching? Does he have an allergy?

By Dr Megan Kelly

Allergic skin conditions are a continuous challenge for vets and pets owners. There are so many variables and potential causes and there is no conclusive test to get a clear cut diagnosis. The most common causes of allergies are flea allergy dermatitis, atopic skin disease and food allergies.

When presented with any skin condition your vet will always rule out bacterial, yeast or fungal infection, and mites. Once these have been treated or ruled out and the itchiness still persists then it is most likely one or a combination of these three conditions.

• Flea allergy dermatitis

Flea allergy is a complex allergic reaction to proteins in the saliva of the flea. It comprises between 50% and 80% of all allergic skin disease in dogs. Just one flea is all that is needed to cause the allergic reaction.

• Atopic dermatitis

Atopy is a genetic predisposition to synthesize IgE against environmental allergens (airborne allergens), such as plants or trees pollens, weeds, mites, dust etc. It comprises about 10 percent of all allergic skin conditions.

The origin of this disease is unknown, although it is shown there is important hereditary predisposition, i.e. allergic parents will probably have allergic offspring. Some breeds have special genetic predisposition to suffer from atopy.

Breeds that commonly suffer from Atopy:

American Staffordshire Terrier, German Shepherd, Boston Terrier, French Bulldog, Boxer, Bull Terrier, English Bulldog, Cairn Terrier, Golden Retriever, Fox Terrier, Dalmatian, Shar Pei, Shih Tzu and West Highland White Terrier.

• Food allergies

This can start at any age from very young to quite old. The most common causes are protein sources which have been consumed by the animal for years without any problems.

The first thing we need to realize when we are treating skin conditions is that we are unlikely to cure the problem we are mainly looking at how best to manage it. Certain factors are easier to manage than others for example it is more difficult to control air borne allergens than it is to control the type of protein your pet eats. So we will start with the things that are the easiest to control.

Since flea allergy dermatitis comprises 50- 80 % of skin allergies I think its advisable to start with eliminating fleas on your pets (all pets in the house) and the environment. Then progress to exclusion diets and removing potential causes of atopy where possible.

1. Flea control: Be aware of other pets visiting your house bringing in fleas. Wash all bedding, mats and blankets. Use a product your vet recommends and make sure you do not miss a treatment. Remember just one flea bite is all that is needed.

1. Exclusion diets: A novel protein and carbohydrate diet is selected and used strictly for a minimum of 2 months. No treats or tit bits. Consider diets with no grains. Ask your vet to discuss all the different options.

1. Restrict contact with allergens: If possible try restricting contact with certain allergens e.g. grass. Vacuum daily, remove rugs and carpets to decrease the dust mite load etc. Use rubber socks or boots if your pet has an allergy to grass. Avoid long grass and rinse your pet with water after walks to decrease the allergen load. Pollens etc adhere to their coat.

Management for all skin conditions no matter what the cause

1. Skin care:  Scratching can traumatise the protective surface of the skin. This will make the skin susceptible to secondary infections. Shampoo weekly with antibacterial, anti-itch, antifungal and emollient shampoos. They contain hydrating agents such as urea and glycerol, and essential fatty acids with double function: to restore the lipid layer of the horny layer avoiding the loss of water, and to avoid dehydration and reduce inflammation. Soothing skin sprays and gels containing herbal preparations are available to soothe and treat skin conditions topically.

1. Skin diets: Various specialising diets are available to improve the skin and coat condition in animals. Hypoallergenic diets are commonly prescribed for allergic animals, and some of the ingredients are fish oil, rich in essential fatty acids (omega 3 and omega 6).  It has been shown that the administration of diets or supplements rich in essential fatty acids is beneficial and helps to control allergy signs, apart from improving the skin barrier function in animals suffering form atopy.

1. Supplements: Herbal and homeopathic preparations to assist with treating skin conditions and supporting the immune system.

1. Other treatments your vet may consider: Cortisone, antihistamines, immunotherapy. Ask your vet about the side effects of long term use of these products.

Remember that some allergies are seasonal and can be worse in certain times of the year.

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