Your dog is itchy and has a hairless region that's red that you think might be an allergy rash. Or maybe he has a red spot from allergies that you're pretty certain was caused by something topical. Whatever it is, you want to be able to treat it.
Instructions
Determine if the rash is indeed caused by an allergic reaction to something. Dogs, like people, get rashes for all sorts of reasons. Your dog may have an insect bite, a hot spot, flea allergy dermatitis, or even an abscess. For example, hot spots are often caused by irritated skin and moisture, which may cause a weepy sore; while this is serious, it is an infection, and not necessarily caused by an allergic reaction. Most allergies are either topical, insect bite, or food-allergy related.
If the rash is caused by a contact allergy, bathe your dog in a gentle hypoallergenic shampoo. Removing the substance from the coat is often enough to help clear up the rash in a few days.
Look for an insect bite. The rash will have a hard bump where the insect bit or stung your dog. Try topical Benadryl to help treat it. Smear some Benadryl on the irritated skin.
Get rid of fleas. Your dog may have flea allergy dermatitis, especially if he has fleas. Give him a bath in a mild shampoo recommended by your veterinarian and use a spot-on topical flea product such as Biospot, Frontline, Advantage or Program to eliminate the fleas.
Put your dog on a hypoallergenic diet. Many skin rashes come from food allergies. Your veterinarian can prescribe a good hypoallergenic diet for your dog. Hypoallergenic dog food has what is called a novel protein source (a meat or other protein source that is not commonly found in pet food) and a novel carbohydrate (usually grain) source. These need to be different because many dogs develop allergies to certain meats and grains. By giving him a grain or meat he hasn't eaten, there's a chance he won't develop an allergy to it. Examples of novel protein sources include venison, duck and certain types of fish. Example of novel carbohydrate sources include potatoes, millet and buckwheat.