Unlike humans, dogs aren't usually stressed out or embarrassed by the silly things they do. When people are anxious or flustered, they sometimes break out in hives. Allergies can cause hives in people as well, and are more likely the cause of your dog's hives. Hives appear as itchy raised red welts, sometimes as a rash, and can be circular or uneven in shape and size. They are either concentrated in one area, or widespread. Treating them is vital to your dog's health and well being.
Remove the source of the hives. This is an important first step because if the cause of the hives is not found and removed, the hives will continue to bloom. The source can be something in the environment with which the dog's body came in contact. Common causes are chemicals used on lawns or carpets, a new pet shampoo or laundry detergent used on bedding. It could be an inhalation allergy caused by pollens and other airborne microscopic substances. The dog could have been bitten by an insect that injected a toxin that triggered the hives. Food allergies are also a common reason dogs break out in hives.
Bathe the dog in a tub of cool water to which oatmeal has been added. There are commercial oatmeal bath and shampoo preparations, but oatmeal found in your pantry works too. There are two methods for preparing an oatmeal bath. Measure a cup of regular oatmeal and place it in the middle of a clean coffee filter. If you don't have one, you can use a piece of pantyhose, cheesecloth or a clean, white sock. Close up the filter and secure it with a rubber band. Toss it in a bathtub of cool water. The other method is to take a cup of oatmeal and process it in a blender or food processor to pulverize it to a fine powder. Sprinkle it over a tub of cool water.
Administer diphenydramine, (brand name Benedryl) to your dog. This can be done in addition to the cool bath. Diphenydramine treats allergy symptoms in humans and most non-human animals such as cats and dogs. Give 1 to 2 mg for every pound the dog weighs. So if your dog weighs 25 pounds, the dosage would be 25 to 50 mg. Diphenydramine comes in a variety of strengths, so check the label carefully. If the hives return, continue to give diphenydramine every eight hours.
Massage the affected areas with an anti-inflammatory cream that contains hydrocortisone. These creams can be found over-the-counter at any drugstore. Your vet may also call the pharmacist and prescribe a stronger cream or an oral steroid such as prednisone. If the cream is unavailable, you can make a paste with cooked oatmeal. Be sure it is completely cooled before using on your dog.