Skin Allergies in Cats

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Allergies are the most common cause of skin disease in cats. They are three main types, but cats can be affected by multiple allergies.  Try Pet Head for Cats

1. Flea Allergy - Fleas cause up to 80% of skin problems in cats.
2. Food Allergy - Reactions to foods or additives cause either skin problems or vomiting and diarrhoea. It is unusual to see both in any one cat.
3. Atopic Dermatitis - Atopic dermatitis is caused by an allergy to house dust mites, pollens or moulds.

Other causes of skin problems include lice or mites, fungal infections, auto-immune or internal diseases and cancers, but these are much less common than allergies.

SYMPTOMS
The hallmark of an allergy is itchiness, although some cats rarely scratch or lick in front of their owners. Furballs or hairs around the tongue, teeth or house may be signs of excessive licking. Some cats will appear to go bald, although the hairs are really being broken off by licking. Fleas can cause small crusts along the back (called miliary dermatitis) whereas crusting and ulcers around the head and neck may suggest food allergies or ear mites. Some cats develop large red, moist and weeping sores (called eosinophilic plaques), on the belly and legs.

FIRST LINE DIAGNOSIS
Your vet will want to rule out lice and mites, and treat any infections before investigating allergic diseases. Some cats scratch and lick where they are experiencing pain so vets also need to rule out arthritis, other pain or cystitis.

1. FLEA ALLERGY
Rigorous flea control should be the first step, irrespective of whether fleas can be found. It only takes a few fleas to set off a reaction in allergic cats. The best products to use on your cat are long-acting sprays and spot-on remedies prescribed by your vet like Frontline, Stronghold or Advantage. Over-the-counter products are ineffective and may even be toxic. Eggs and larvae in carpets and furnishings should also be treated. Sprays with an insecticide and growth inhibitor, such as Indorex, Acclaim, Canovel Pet Bedding and others, are most effective for these. There is also another product, Program, (available as a pill, a liquid or an injection) which does not kill fleas but stops their eggs hatching in the first place. This prevents fleas from re-establishing themselves. All these products are available from your vet. Flea control trials usually last for 4-5 weeks. Remember to treat all the dogs and cats in the house and continue indefinitely ­ stop treatment and the fleas will return.

REFERRAL
Just as in human medicine, there are general and specialist vets. There are a number of veterinary dermatologists throughout the UK. Referral appointments can only be made through your own vet, who may suggest a referral, or you can ask them to make an appointment for a specialist opinion

2.FOOD ALLERGIES
The next step is to investigate food allergy. Your vet will recommend a trial diet using foods new to your cat. Home cooked diets using a single protein (e.g. meat or fish) and carbohydrate (e.g. rice or potatoes) with water to drink are best. Give the same amount as tinned or half-again as much as dry foods. Hypoallergenic diets are available from your vet if necessary. Other cat-foods contain a variety of ingredients that vary from batch to batch and are not suitable. Trial diets should be fed for six weeks. Cats should not be fed anything else during the trial. Cats that hunt or are fed elsewhere may need to be kept indoors.

Allergic diseases will wax and wane, so an improvement does not necessarily mean the cat has food allergy. A relapse within 1-2 weeks on the original diet confirms a food allergy. Once stable again on the trial diet, introduce ingredients such as beef, lamb, dairy products etc. one at a time to discover which the cat reacts to. These can then be avoided. Alternatively, a prescription hypoallergenic diet can be tried. Zennor, the cat in the photo, had a food allergy and recovered completely when given a prescription hypoallergenic diet

3. ATOPY OR ATOPIC DERMATITIS
If skin problems persist then allergy tests should be used to identify what your cat is allergic to - the allergens - for treatment or avoidance. Allergy tests should be carried out by an experienced veterinary dermatologist.
a) Skin testing. Cats are sedated and the fur on the side of the chest clipped. Several dust mite, insect, pollen and mould extracts are injected and any reactions noted. Most reactions occur within 20 minutes although some may take 12-24 hours. Skin tests are very specific, but some cats have negative tests.
b) Serological tests. A blood sample is taken and sent off for laboratory testing. The tests show which allergens are producing antibodies in the blood. Serological tests are not quite as exact as skin tests, and are not necessarily cheaper. They are useful if skin tests fail, or if the cat's skin is in such bad condition that a skin test cannot be run.

TREATMENT
1. Basic Treatment
Thorough flea control is important in all cases of allergic skin disease. Regular worming and a high quality balanced diet will also be of benefit. Cat Shampoo
2. Lifestyle Management
Some allergens can be avoided. Dust mites and pollens are ubiquitous, but keeping cats out of bedrooms and carpeted rooms, using solid or washable cat-beds, vacuum cleaners with filters and improving ventilation will help.
3. Immunotherapy
Most veterinary dermatologists use immunotherapy to desensitise your cat by giving regular injections of allergens identified by skin or blood tests. Most cats tolerate the injections very well. Your vet will usually administer the first few injections in the unlikely chance of an allergic shock, or anaphylactic, reaction, but most owners give the injections at home thereafter. Mild itching and injection site nodules are minor problems. Approximately two thirds of cases respond to immunotherapy.
4. Anti-inflammatory Treatment
Anti-inflammatory treatment may be necessary if your cat does not respond to immunotherapy. Short-term treatment may be used during flea control or food trials.

a) Antihistamines
Many of these drugs are available from pharmacists, but the doses in cats are different from people, and they should only used under veterinary supervision. Your vet will try 3-4 drugs to select the most effective. Side effects are uncommon, but include sedation and vomiting. Only about 50% of cats respond to antihistamines, although the response is better if they are combined with essential fatty acids.
b) Essential Fatty Acids
These are fish and plant (e.g. Evening Primrose or Borage) oils. Veterinary products are preferred unlike cheaper brands that vary from batch to batch. The initial course is usually eight weeks, although again no more than 50% of cases respond.
c) Steroids 
These are cheap and effective, but can have serious side effects (including weight gain, excessive drinking and urinating, infections, diabetes, liver and skin problems) and are generally used as a last resort. Many cats tolerate low doses of steroids given on alternate days quite well. Using other treatments often reduces the dose required. Cats on long-term steroids should have regular check ups.

5. Other Treatment Options
Without controlled studies it is difficult to know if alternative remedies are of any benefit. Many human remedies can be quite toxic in cats and should only be given under veterinary supervision. Female sex hormones (e.g. Ovarid®) have little role in feline dermatology. Serious side effects are common, and these drugs should only be used to treat specific conditions by an experienced veterinary dermatologist. Any alternative remedies should be passed by the vet before being used.