Dogs and cats can develop skin rashes from a number of causes, including allergies, fleas, and bacterial or fungal infections. Sometimes a rash seems to pop up overnight as a red, moist, weeping area on the skin, informally called a "hot spot."

The formal name for hot spots is acute moist dermatitis. They are most common in long-haired dogs, but any breed can be affected. Fleas and allergies are the most common causes, but any itchy irritation-even serious hair matting-can get a hot spot started. Pets lick the itchy area intensely, often when no one is looking, until it becomes red, raw, and moist. Bacteria then often move in and infect the damaged area, making the problem worse.

Fortunately, hot spots are usually superficial and look much worse than they really are. Your veterinarian will clip away the hair so that the wound can dry out, and then clean the area with an appropriate antibacterial soap or solution. Follow-up care at home usually includes cleaning, topical medications, and sometimes oral antibiotics or corticosteroids. In addition, the underlying cause of the hot spot must be addressed by controlling fleas, allergies, infections, hair mats, etc.

Q&A

What is a hot spot?

A hot spot, also known as acute moist dermatitis, is a superficial, red, moist, weeping rash on the skin.

What causes a hot spot?

Fleas and allergies are the most common causes, but any itchy irritation—even serious hair matting—can get a hot spot started.  Pets lick the itchy area intensely until it becomes red, raw, moist, and infected. 

How is this condition treated?

Your veterinarian can clip away the hair, clean the area, and prescribe appropriate therapy, such as topical medications and (sometimes) oral antibiotics or corticosteroids.  In addition, the underlying cause of the hot spot must be addressed by controlling fleas, allergies, infections, hair mats, etc.