Introduction To Allergic Skin Disease In Dogs

Allergic skin disease is characterized by itching (pruritis), dermatitis, eczema, and poor coat quality. Recent theories suggest that allergic skin disease results from the summation, adding together, of the various causes of allergy. We all recognize that animals can be allergic or sensitive to things which come into contact with their skin for example fleas, flea saliva, and flea dirt. However there are other sources of things to which animals may become sensitized, these include things an animal may breath and things an animal may eat. So now we have three groups of particles (allergens) to which animals can become sensitized. These are called ; a) contact, b) inhaled, c) ingested allergens. If the sum of these allergen sources (a + b + c) exceeds a certain point (the puritic threshold) then the animal will itch. Whilst it is difficult to control what an animal breathes, we can have an influence on what comes into contact with their skin and what they eat. If we could remove some of the allergic stimulation from the animal then we may reach a point where the sum of the allergenic sources is below the puritic threshold and the animal will stop itching.

An alternative approach is to use drugs which push the pruritic threshold up so the sum of the allergen sources no longer exceeds it. This is how steroids are thought to work, and while they are very effective there may be a price to be paid in the form of potential side-effects.

The best approach with any allergic disease is to avoid the triggering cause. Hypoallergenic diets are those containing protein, carbohydrate and preservatives to which your pet is unlikely to be sensitized. Most commonly these food contain protein sources such as lamb or chicken and carbohydrate sources such as rice or tapioca. Any additions to these diets may well be counter-productive. Owners whose pets are on such diets will often note that if their pet gets a mouthful of another food it may itch for 3-4d while it passes through the animal.

Occasionally even with the use of hypoallergenic diets and good control of contact allergens by establishing flea control, regular baths, and minimizing environmental allergens like house dust, a pet will still itch. There are still many things that can be done without reverting to the use of steroids. These include antihistamines and essential fatty acids such as evening primrose oil which work very well together. Controlling any secondary bacterial skin infection with antibiotics can relieve many symptoms. Some practitioners find the use of homoeopathy or Aloe Vera useful. An approach which can be very useful is desensitization. To desensitize an animal you have to establish what it is allergic to, this can be done either with a skin test or a blood test. Once you have a list of allergens to which the animal is sensitive these can be combined in a solution for desensitizing that individual animal. The solution is injected into the animal at very low doses initially and the dose is gradually increased over about a month so the individuals allergic response is slowly overwhelmed. There is a danger that the animal could produce a massive allergic response (anaphylactic shock) after any of the injections so it must be monitored for 30min after each treatment. Eventually the animal needs just one injection a month to keep it allergic response quietened down (immunomodulation).