Managing the dog with skin allergy
Dogs often develop signs of skin allergy as young adults, commonly from two years of age. As many as one in six dogs may develop skin allergies. Unfortunately, once signs develop it is likely that the skin problems will occur for life. Skin allergies cause many different skin problems and require different treatments for each individual and at different times. Skin allergies are frustrating to treat as periodic relapses and secondary problems are common. The aim of therapy is to control signs of irritation without resorting to the use of steroid drugs, where possible.
REDUCING THE ITCH THRESHOLD
Every pet will tolerate some allergic skin reaction without discomfort. However, if the stimulus is too strong, the skin becomes red and itchy – the itch threshold has been exceeded. Stimuli that cause excessive itching are called flare factors. Dogs with skin allergies may have minimal irritation if flare factors are properly controlled.
Meticulous flea control is essential, using both insecticidal treatments on the dog and environmental flea control in the house – integrated flea control. Flea control should be used all year round and all pets in the house should be treated. Please ask the nurses about the most appropriate type of flea control for your needs.
Control secondary infections. Secondary infections may be bacterial, fungal or parasitic and each type of infection needs specific treatment. All allergic dogs will develop secondary infections from time to time. Antibiotics for bacterial skin infections have to be given at high dosages until the skin appears normal and then for a further two weeks. This commonly requires 4-8 weeks treatment and can be costly in a large breed dog. Elimination of secondary bacterial infections is critical for the successful management of allergic dogs.
Keep the ears clean. Most allergic dogs will develop signs of ear irritation. Regular treatment and cleaning will reduce the itch threshold.
Fatty acid supplementation has been shown to make the skin resistant to inflammation. Omega-3 fatty acid supplements are widely available in many forms. We recommend a 1000mg Evening Primrose Oil capsule daily (500mg for very small dogs). Supplementation should start 6 weeks prior to the start of the itch season.
Antihistamines are very safe drugs. They work better if given at high dosages, if used with fatty acid supplementation and if treatment is started 6 weeks before the period of highest risk.
Recently, the powerful anti-inflammatory drug Cyclosporin has become available to treat allergic dogs. This product is given once daily for a month and is then given every few days as required. This treatment has potentially severe side-effects and is best reserved for the more severe cases of skin allergy. Cyclosporin treatment is also expensive compared with other treatment options.
OTHER MANAGEMENT OPTIONS
EXCLUSION DIETS
The use of diets that contain novel protein sources (such as seafish) excludes the possibility of allergic reactions in the gut. Dietary allergy is thought to complicate skin disease in about 10-20% of cases and act as a flare factor for skin disease. A trial of an exclusion diet is worthwhile in any pet with severe skin allergy or allergy unresponsive to standard treatments. However exclusion diets are just that. No other food should be offered other than the special diet for a period of 6-8 weeks. This is difficult in dogs, and failures may occur due to dogs stealing food or scrounging titbits. If an exclusion diet trial is tried, everybody in the household has to be motivated to ensure success.
Although, many pet foods are marketed for skin allergies, it is now recognised that many such diets contain protein from several sources. These diets are not exclusion diets and will not be effective in cases of food allergy. Please check with the nurses as to the best exclusion diet for your pet. In difficult cases, a hydrolysed diet that is incapable of causing allergy can be used (Hill’s Z/D)
DESENSITISATION
The allergens causing your pet’s skin reaction can be detected by intra-dermal skin testing or blood testing. A “vaccine” can then be made up for your pet that overwhelms the allergic response. This would seem an ideal treatment, avoiding any requirement for drug therapy. However, testing is expensive, some dogs may not react to commonly tested allergens and desensitisation does not produce improvement in every case. An initial trial period of one year is required and desensitising injections are required for life. Desensitising injections also have the ability to cause extreme and life-threatening allergic reactions, although this would seem to be a very rare occurrence in dogs.
CYCLOSPORINE THERAPY (ATOPICA)
Cyclosporine is a powerful drug most often used to prevent organ rejection after transplants. However, at lower doses it greatly decreases inflammation of the skin. The drug is given once daily at least 2 hours before or after feeding. It is a slow-acting drug and improvements are not usually seen for a few weeks. Once the skin is cooler, the drug is given every second day and then every third or fourth day to keep the dog symptom free. Atopica cannot be used in pets under 6 months of age or less than 2 Kg bodyweight. Although, a powerful drug, it is though that side-effects are less than with steroid use. Atopica can be used for a year while a course of desensitisation injections is proceeding.
AVOIDANCE
The commonest cause of skin allergy in dogs is house dust mite faeces. This allergen is concentrated in areas of the house with the most soft furnishings and is at its highest in beds and in bedrooms. Some allergic dogs may benefit by being kept off the beds, sleeping in the areas of house with hard floors or outside. The bedding should be washed frequently and can be covered with a pillow cover for asthmatics (available at all chemist shops). Some pets that react to grass, moulds or pollens may benefit from having their feet washed on return from walks. Generally, efforts to keep dogs away from the allergic stimulus are poorly rewarded.
THE NERVOUS PET
Some nervous pets may become very anxious as a result of skin irritation and may traumatise the skin by biting or scratching, thus making the skin problem worse. A mild tranquiliser at bedtime can be used during the worst periods of itching.
