Contact Dermatitis in Dogs
Contact dermatitis may be caused by an allergy, or it may simply mean that your pet has touched something that has irritated its skin, such as the sap in poison ivy, or salt on a road. It is difficult to distinguish one from the other because the symptoms usually appear the same. Allergic reactions require a previous, sensitizing experience with the irritant. The next contact with the irritant is when symptoms occur. Both dogs and cats can suffer from allergic contact dermatitis and irritant contact dermatitis. It can occur at any age, and is a direct result of the irritating nature of the offending compound.
There is an increased risk of allergic reaction in German Shepherds, French Poodles, Wire-haired Fox Terriers, Scottish Terriers, West Highland White Terriers, and Golden Retrievers. Some dogs have reactive dermatitis from medications. An overall reaction, as from shampoo, is uncommon. If it seems to occur at certain seasons, it indicates that the offending source is a plant or outdoor compound.
The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.
Symptoms and Types
Dogs suffering from contact dermatitis will most likely suffer from rashes and/or bumps which occur on the skin that has come in contact with the ground (i.e., the chin, neck, chest, abdomen, groin, anal area, scrotum, tail, and between the toes). These rashes may stop abruptly at the hairline. Other common symptoms include itching, which is usually severe, and swelling.
Factors and/or substances that have been reported to be skin irritants are:
- Mulch/Cedar chips
- Rough surfaces
- Floor waxes
- Carpet and litter deodorizers
- Sensitivity to the sun/heat
- Topical agents
- Food allergy
- Insect bites
- Bacterial infection
- Fungal infection (e.g., ringworm)
- Flea collars
- Parasitic hypersensitivity or infestation (e.g., mites, fleas)
- Insecticides, including newer topical flea treatments
Your veterinarian's first task will be to find out what the offending irritant is. The symptoms cannot be treated until tests are completed, to avoid aggravating the condition. There are several ways to approach tracking down the triggers. One is to do what is called a patch test: the suspected substance is placed on a patch and taped to the skin for 48 hours. Any reaction is then assessed. The second is to remove the pet from the offending environment for a period of time and then return it to the environment, monitoring what happens and whether it has had any impact one way or the other.
Your veterinarian will also want to perform bacterial cultures. A clip of hair may be taken from a patch in an area that is not affected, applied to a sample of the suspected antigen, and observed for possible reaction. Skin biopsies are also sometimes required.