Celia Haddon - Cat Expert

Understanding animals through their behaviour

SKIN ALLERGIES IN DOGS

Written with the help of Dr Tim Nuttall,  co-author of Skin Diseases of the Dog and Cat, and author of Veterinary Advice on Skin Diseases in Dogs.

INTRODUCTION

Allergies are the most common cause of skin disease in dogs. There are three main types, but dogs can be affected by multiple allergies.
1. Food Allergy.
2. Atopic Dermatitis
3. Contact Allergy

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

SYMPTOMS

Skin allergies are common in dogs. There may be all or some of these symptoms. A general itchiness so that the dog is chewing, licking and scratching in a frenzied way, sometimes even stopping to scratch during eating or during a walk. The hair is chewed away to leave bald patches. The skin becomes red and inflamed and in extreme cases the skin is broken. The damaged skin eventually becomes darkened and thickened. Paws are red and moist between the toes and cysts may form. The back of the paw above the stopper pad, the equivalent of the human wrist, goes bald. The damaged areas then get bacterial or fungal infections and may begin to smell. Recurrent ear infections mean the dog is scratching or shaking its ears. There may be discharges from the ears.

FIRST LINE DIAGNOSIS

Your vet will want to rule out parasitic infections like fleas and mites. Even if there are no visible signs of fleas, the dog should be treated with prescription flea medicines. Over the counter flea preparations are not effective enough. Treat the house and all other animals in the household with products containing an insecticide and growth inhibitor. Proper flea control is important, even if the cause is not direct allergy to flea bites. Any bacterial or fungal skin infections must also be treated. If these first line treatments succeed, then the skin problems are probably not due to an allergy.

REFERRAL
At this point, it is usually a good idea to ask your vet to refer you to a veterinary skin specialist if the skin is no better. This is the same principle as a GP referring a patient to a consultant. Referral must be made through your own vet, but most vets will be happy to do so and indeed cannot refuse to do so. There are three main causes of skin allergies – food allergy; atopic dermatitis; contact allergy. Food allergy and atopic dermatitis are often found in combination and usually start with an itch, which becomes a rash. The skin inflammation may be anywhere in the body. Contact allergy usually starts with a rash, which later becomes an itch. The skin inflammation is on an area of the body like paws or tummy which is in contact with something causing the allergy.

1. FOOD ALLERGIES
Dogs can become allergy to something they have been eating for years without trouble. They rarely, if ever, become allergic to a completely new food. a) The specialist will put your dog on to a completely new diet, either a commercial one or a home cooked one like, say, fish and potatoes. This is sometimes called an exclusion diet. For up to six weeks the dog must eat NOTHING else _ no treats, no chews, no bones. However, if the skin gets better, this indicates but does not confirm it was a food allergy. b) The next stage is to put the dog back on its ordinary diet for up to two weeks. This is called a re-challenge. If the skin inflammation returns, then this is proof that the diet was causing it. c) Your dog will go back on the exclusion diet and a new ingredient will be added, one at a time. If the new ingredient causes skin inflammation, then the cause of the allergy is identified. The cause is identified, the specialist will help you choose a new diet for your dog – probably a commercial diet which excludes the problematic ingredients.

Sometimes this process is short circuited, and after feeding the exclusion diet, the owner is helped to try out different commercial diets with varying ingredients to see if one can be fed without causing the allergy.

2. ATOPY OR ATOPIC DERMATITIS
The dog is reacting to something in the environment which is normally harmless. Possible causes or allergens can include dust-mites, skin dander, insects, pollens or moulds. The specialist will normally do one or both of these tests. If the dog has already been given steroids, then a delay may be necessary till these leave the body. a) Skin testing. Your dog is given a sedative then an A5 size patch of fur from the side of the chest is shaved. Up to sixty possible allergens are injected into the skin. After 20 minutes the skin will redden at the spot where the allergen was injecting. This shows which substances are causing the allergy. Some sites may react after 24 hours. The dermatologist will usually ask you to watch out for these and let him or her know. 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 but are useful if skin tests fail, or if the dog’s skin is in such bad condition that a skin test cannot be run.

TREATMENT

Allergies cannot be cured and require lifelong treatment. However, with the appropriate treatments the prognosis is generally very good. There must be proper flea control and any skin infections must be treated. If a food allergy is partly or wholly involved, a non allergic diet must be chosen.

1. Immunotherapy 
If the cause of the allergy has been identified, then the dog can be treated by injecting it with increasing amounts of the allergen. This will take up to ten months of treatment and works in two thirds of the cases. The initial injections will be given at a vet’s surgery, to make sure the dog doesn’t have an allergic shock reaction. While this treatment is going on, your dog will continue to need treatment with anti-inflammatory drugs like antihistamines or steroids. Shampoos and ear cleaners will also be useful. If immunotherapy isn’t suitable or doesn’t work, then the allergy has to be managed rather than cured. This means a system of trying various things to see which works best.

2. Anti-inflammatory treatment

a) Antihistamines. 
These are the same drugs used to treat allergies and sea sickness in humans, although they should only be given under veterinary supervision. Your vet may want to try several different drugs to find which works the best. They are generally safe but may make the dog sleepy or cause tummy upsets. Unfortunately, only 50% of cases seem to respond.

b) Essential Fatty Acids 
These are fish and plant (e.g. Evening Primrose or Borage) oils. Veterinary products are preferred over cheaper brands that vary from batch to batch. The initial course is usually eight weeks, as they take time to have an effect, although again no more than 50% of cases tend to respond.

b) Steroids
These are very effective in stopping skin inflammation but in the long run may have side effects. Given by mouth in as low a dose as possible and only every other day they are usually well tolerated, although dogs on steroids should have regular check ups.

c) Local applications
Peppermint oil, menthol compounds and camomile lotions can be soothing when put on skin that is acutely inflamed.

3. Lifestyle management 
The aim is to reduce the allergens in the dog’s environment. This can involve anti-dust-mite sprays, heavy hoovering, plastic dog beds, regular washing of bedding, reducing the heat in the house (dust-mites thrive in heat); removing carpets, keeping the dog out of bedrooms.

3. CONTACT ALLERGY

This is rare. It can be caused by carpet dyes, household cleaners, grass or flower pollen. Other possible causes include a reaction to eye drops, ear drops or shampoos. It is usually found on the underside of paws, the underside of the body, or any part of the dog which has been in direct contact with the allergen.

Diagnosis
a) The dog is hospitalised for up to a week away from its environment. If the skin improves, then a contact allergy may be suspected. b) Patch testing. The dog is sedated and a large area of skin on the side of the body is shaved. The suspect allergens are applied to the skin and secured there by a piece of gauze. The area is bandaged and left for two to three days. (The dog has to wear an Elizabeth collar to stop it tearing off the bandage.) The skin will become inflamed where it has been in contact with an allergen.

TREATMENT
If possible the dog is kept from all contact with the allergen. This may involve getting rid of carpets or avoiding certain places during the pollen season. If this isn’t possible then the dog may be treated with steroids either in pill form or in ointment form
Allergy testing. TLC Pet Allergy Testing http://www.animal-allergy.com

Vedbed now has an inbuilt Permafresh which is said to inhibit dust mites , might be good for dogs who are allergic to dust mites.

COPYRIGHT.

These notes are my copyright. I am also usually happy to have the exact words reproduced on websites, in return for a link, my name, and if permission is asked beforehand. I like to check the websites where it might be used. Email me via this website for permission which will usually be given. Organisations wishing to use them in print should contact me via this website. Copyright © 2007 Celia Haddon. All Rights Reserved.

Safety notice.

All normal safety precautions should be taken when dealing with animals. The advice in this section should be taken only at the owner’s own risk. All sick animals should be seen by a vet.

General advice of the kind found in this website is no substitute for an individual consultation with a vet or qualified behaviourist working on a vet’s referral.

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