Red, hot, irritated and moist spots on your dog's coat are commonly called hot spots. They're also called acute moist dermatitis. Generally, any time the skin becomes irritated, a hot spot can develop. With prompt treatment, hot spots usually clear up relatively quickly.
Stop the Spread
Hot spots spread rapidly, so the first step in the healing process is to put a stop to the condition that caused the hot spots in the first place. Make a trip to the veterinarian. The dog may need flea or tick treatment, or a change in diet to deal with allergies, or extra exercise to alleviate boredom and stress. In some cases, the cause of the hot spot will be obvious, but in many cases the vet will do tests to determine a firm diagnosis.
Heal the Wound
Hot spots can spread rapidly because of bacteria on the skin and because of your dog's desire to scratch and bite the area for relief. To clear up a hot spot as quickly as possible, have a professional trim the hair around the hot spot to expose bare skin. This makes it easier to medicate the wound and allows air circulation, which speeds healing. Clean the wound with a gentle cleanser, and coat with antibiotic ointment. Repeat this process several times a day and you will notice an improvement in the wound within a day or so.
The inflamed, irritated hot spot should dry up and appear much better within a few days of treatment. Hair regrowth, however, will take a while. You may need to keep your dog in an Elizabethan collar so he doesn't lick and bite at the wound while it heals, which would slow healing. Talk to your veterinarian about dietary supplements that contain essential fatty acids to help hair grow in and reduce itching. Your veterinarian may recommend corticosteroids or antihistamines to reduce itching so your dog will leave the hot spot alone while it heals.
Dogs who have experienced hot spots in the past may be more prone to developing them again. To reduce the risk of your dog developing hot spots repeatedly, make sure he stays on effective flea control, provide adequate exercise and play to reduce stress and boredom, and groom him regularly.