Flea Allergic Skin Disease

text - Jenny King and David Vawer

Allergies in General

Alleries of various types are some of the most common conditions affecting dogs, but seem to appear less so in cats. In the allergic state, the pet's immune system "overreacts" to foreign substances, known as allergens or antigens, to which it is exposed. These overreactions are manifested in three ways.

The most common is itching of the skin, either localised (one area), or generalised (all over the pet).

A second manifestation involves the respiratory system and may result in coughing, sneezing and wheezing. Sometimes, there may be an associated nasal or ocular discharge.

The third manifestation involves the digestive system, resulting in vomiting or diarrhoea.

The specific response that occurs is related to the type of allergy present.

There are at least five known types of allergy in the dog: contact, flea, food, bacterial and inhalant. Each of these has some common features which are shared with the others, But there are also some features unique to each type.

In this article we aim to concentrate specifically on flea induced allergy.

The Problem

Original image courtesy of Bayer UK Ltd.

In spite of common belief, a normal dog or cat experiences only minor skin irritation in response to flea bites. Even in the presence of dozens of fleas, there will appear to be very little itching. On the other hand, the flea allergic pet has a severe itch producing reaction to flea bites. This occurs because of the development of an allergic response to the flea's saliva which is deposited under the skin when the flea feeds (see Fleas and Their Control). Just one fleabite in a sensitised pet will cause intense itching of a long lasting nature. The animal's response to the intense itching is to chew, lick or scratch. This causes hair loss and the self infliction can lead to open sores and scabs on the skin. This allows a secondary bacterial infection to begin. The area most commonly involved is the rump (just in front of and including the tail) followed closely by the areas around the neck and along the back. This is probably because fleas find this part of the dog more desirable. Many flea allergic dogs will also chew the hair from their legs and feet.

If not treated promptly, then the animal can lose the majority of its hair and become a horrifying sight. The skin being chronically insulted becomes thickened and elephantine. The worse areas seep serum, which matts the little hair which remains and caused foul smelling sticky areas. The least touch of the skin can induce a marked scratch reflex where the hind claws can cause dramatic self infliction with bleeding sores. The pet is off its food, often running a temperature and feels very ill.

Unfortunately all Veterinary Surgeons in practice see cases at this level on a regular basis, and in many of these cases the owner reports that they have "tried everything" to treat it without success, but indignantly also state that "my pet never has fleas!"

Treatment

STRICT FLEA CONTROL.

This is the most important treatment. It will need to be strictly enforced because just one flea bite can cause a significant reaction in your pet.

Full details of the type of products which are available are detailed in our article"Fleas and their Control" It is essential, however that you discuss the situation with your Veterinary Surgeon who will advise you fully as to the course of action to take in your particular case. Flea control will however need to encompass to main areas.

1. Fleas on your pet
2. Fleas in the environment.

In mild cases this is all that may need to be done, but the majority of problems will need additional treatment.

Steroids.

Whilst flea control is being accomplished, corticosteroids (cortisone like drugs) can be used to block the allergic reaction and give relief. This is often a necessary part of dealing with a flea allergy. Some pets respond better to injections and others to oral medication. Very occasionally a topical cream is used.

Animals can have side effects with steroids, especially if they are used for a long period of time. The aim, therefore, is to administer the smallest amount of steroid to keep the patient comfortable. Your pet should always be weaned off the steroid when treatment is terminated.

Antihistamines.

These aim to block the effect of the chemicals produced in the local response. The response in our pets is very variable. These will give relief to some cases, and may be used in addition to steroids to make the dose of steroid as low as possible. They are also used in patients, which cannot have steroids, e.g. diabetics.

Evening Primrose Oil.

This is an excellent natural anti-inflammatory for the skin. It can be used safely in the long term. Many dogs with chronic skin problems have a much happier life when taking evening primrose oil. It does take a couple of months to see the benefits, but is well worth persevering if your dog has an allergy problem.

Antibiotics.

If the dog has a secondary skin infection with the allergy, then antibiotics will also be given. High levels are often used in the skin and courses of antibiotics may need to continue for several weeks.

Desensitisation.

Some dogs can be desensitised to the adverse effects of flea bites. Flea saliva extract (flea antigen) is injected into the dog in tiny amounts over a prolonged period of time. This is an attempt to reprogram the dogs immune system so it no longer overreacts to flea bites. If successful, itching no longer occurs or is less intense when the dog is bitten. However, this approach is usually only successful in around 50% of cases.