What are allergies, and how do they affect dogs?
One of the most common conditions affecting dogs is allergy. In the allergic
state, the dog's immune system "overreacts" to foreign substances (allergens
or antigens) to which it is exposed. These overreactions are manifested in three
ways. The most common is itching of the skin, either localized (one area) or
generalized (all over the dog). Another manifestation involves the respiratory
system and may result in coughing, sneezing, and/or wheezing. Sometimes, there
may be an associated nasal or ocular (eye) discharge. The third manifestation
involves the digestive system, resulting in vomiting or diarrhea. The specific
response that occurs is related to the type of allergy present.
Does that mean that there are several types of allergies?
There are at least five known types of allergies in the dog: contact, flea,
food, bacterial, and inhalant. Each of these has some common features and also
there are some unique features.
What is meant by the term flea allergy?
In spite of common belief, a normal dog experiences only minor skin irritation
in response to flea bites. Even in the presence of dozens of fleas, there will
be very little itching. On the other hand, the flea allergic dog has a severe,
itch-producing reaction to flea bites. This occurs because the dog develops
an allergic response to the flea's saliva. When the dog is bitten, flea saliva
is deposited in the skin. Just one bite causes intense itching and this is of
a long lasting nature.
What does this reaction do to the dog?
The dog's response to the intense itching is to chew, lick, or scratch. This
causes hair loss and can lead to open sores or scabs on the skin, allowing a
secondary bacterial infection to begin. The area most commonly involved is over
the rump (just in front of the tail). This is probably because fleas find this
part of the dog more desirable. Many flea-allergic dogs also chew or lick the
hair off of their legs.
What is the proper treatment?
The most important treatment for flea allergy is to get the dog away from
all fleas. Therefore, strict flea control is mandatory and this involves ensuring
the dog is flea-free and also removing fleas from the environment. There are
many products available for flea control, and many work in entirely different
manners. In some cases, multiple products may be needed. Some are used on the
dog and some on the dog's environment. Unfortunately, complete flea control
is sometimes difficult, particularly with dogs living outdoors in summertime
when the weather is warm and humid, where a new population of fleas can hatch
out every 14-21 days. Some dogs can be desensitized 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
dog's 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 only successful in approximately 50% of cases.
When strict flea control is not possible, corticosteroids (or "cortisone"
or "steroids") can be used to block the allergic reaction and give relief. This
is often a necessary part of dealing with a flea allergy. Some dogs respond
best to long-acting injections and others to oral medication. Dogs are more
resistant to the side-effects of steroids than humans, but significant side-effects
can occur. For this reason, the goal is to administer the smallest amount of
steroid needed to keep the dog comfortable. Some dogs develop a secondary bacterial
infection in the skin. When this occurs, appropriate antibiotics must be used
and steroid therapy reduced even further.
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