Acute Moist Dermatitis (“Hot Spots”)
ABOUT THE DIAGNOSIS
“Hot spots,” also called acute moist dermatitis, are rapidly developing skin sores under the haircoat. They are common in thick-coated or long-haired dogs, less so in cats. They most often develop in areas where the haircoat is heavy, such as the back, tail base, and side of the thigh, neck, or face. Hot spots tend to occur more frequently in hot, humid weather. The dog often will scratch or chew at the area, although it can be quite painful (the condition is also called pyotraumatic dermatitis for this reason). When the hair is parted, the skin is seen to be moist and reddened. A pus-like discharge coats the skin and the base of the hairs.
Hot spots begin with a superficial skin injury that causes some moisture to be caught under the haircoat. Bacteria grow in the fluid, causing more skin inflammation, and the affected area rapidly expands as more fluid oozes from the skin, promoting more bacterial growth. The speed of onset of hot spots is often striking, and a large and painful lesion can develop from previously normal skin in a few hours. Fortunately, other than being uncomfortable, hot spots are not life-threatening and they tend to heal very well.
LIVING WITH THE DIAGNOSIS
Several skin conditions may be underlying causes of hot spots. Anything that causes skin injury or encourages the dog to scratch or chew its skin may start the disease process. Skin parasites such as fleas, ticks, or mange mites; allergies; hair mats; or foreign material caught in the coat are common inciting factors. Preventing reoccurrence of hot spots involves controlling (and, ideally, eliminating) these conditions.
The most important step in treatment is to clip away the hair in the area and then clean the skin of all discharge with a mild antiseptic. The hair should be clipped for at least 1 inch (2-3 cm) beyond the edge of the visible lesion or sore. This is best done with electric animal hair clippers, since scissors often damage or cut the skin of dogs with acute moist dermatitis—avoid doing this hair clipping at home. Your veterinarian may need to sedate your pet for this step if the area is painful, because the skin may be excruciatingly sensitive. After the area is clean, an astringent (drying agent) may be used on the inflamed skin. Preparations containing an antibiotic or antiseptic are applied directly to the area to stop bacterial growth; these topical medications also often contain an analgesic or corticosteroid to alleviate pain. Spray-on products are preferred over ointments. Most hot spots heal rapidly (days) since the infection is only on the surface of the skin.
Some hot spots are associated with a deeper skin infection. In these cases, red, raised bumps often are found scattered in the healthy skin surrounding the hot spot. Golden retrievers seem more prone to this form than other breeds. Antibiotics given by mouth every day for 2 weeks or more are needed to cure this type of hot spot, in addition to the treatment mentioned above
- Keep your pet free of skin parasites, especially fleas.
- Groom long- or thick-coated pets regularly; remove foreign bodies such as plant material from the haircoat, so these do not cause mats nor penetrate the skin directly.
- Treat underlying skin diseases, such as allergies, if present.
- If a hot spot develops, have it treated immediately and use medications as directed.
- Expect that over the first 48 hours of beginning treatment, the hot spot will look “quieter”: less red, with less fluid oozing from its surface, and it should be less painful. Scabbing and return of normal skin usually occur over a 7-10–day period after that.
- Consult with a veterinarian specialized in skin disorders (veterinary dermatologist; see www.acvd.org) if acute moist dermatitis is a recurrent or severe problem. These specialists are best able to identify triggering causes and to prescribe the best treatments
- Do not touch the hot spot directly with your fingers except to apply medication (and then, use disposable latex medical gloves). Touching a fresh hot spot can be painful and can carry bacteria into it, causing an infection.
- Do not apply medication to the sore without first clipping and cleaning the area.
- Do not cut the hair over a new hot spot using scissors, as this is a common cause of severe skin injury (the scissors cut the skin) in dogs.
WHEN TO CALL YOUR VETERINARIAN
- After treatment, if the area still looks red after 48 hours, or if the problem is spreading to new areas of skin
SIGNS TO WATCH FOR
- Intense scratching or chewing at an area, sometimes accompanied with whimpering
From Cohn and Côté: Clinical Veterinary Advisor, 4th edition. Copyright © 2020 by Elsevier Inc. All rights reserved