Pyotraumatic dermatitis (hot spots)
Hot spots are a result of self-trauma. In an attempt to alleviate some pain or itch, the dog scratches and bites at himself. The intense biting and chewing can produce large lesions withing hours. The majority of cases are complications of allergies, but there are many other possible causes, including:
- Parasites (mites, lice)
- Anal sac problems
- Ear infections
- Skin irritants
- Dirty, unkempt coat
- Painful musculoskeletal diseases
Dogs with heavy coats are most prone to hot spots, including Golden and Labrador Retrievers, Collies, German Shepherds, and St. Bernards. The problem may be related to lack of ventilation through the hair.
The typical lesion is red and moist. There is a clear line between the hot spot and healthy skin, and the hair is lost over the lesion. This photo of a small hot spot on the inner thigh of a dog shows a typical lesion. You can see the lighter, greenish yellow center areas that are infected. There are usually bacteria colonizing the surface of the skin. In some cases, and particularly some breeds like Golden Retrievers, there may be very deep-seated infection in the follicles (called "furunculosis") that may take weeks to resolve with antibiotics.
Below is a good example of why hot spots are sometimes referred to as "iceberg" lesions. This Golden Retriever had very sore ears and some crusting on the cheek. When we started shaving the hair, the true extent of the lesion was revealed. This is a common presentation for hot spots - they are very difficult to assess until the hair is removed. (This dog was very well sedated for this procedure. She is a good example of why most dogs with hotspots ought to be sedated before attempting to clip and clean these lesions - they are quite painful.) The last photo is the same dog after 2 weeks of therapy.
How is a hot spot treated?
- Addressing underlying problems. The most important part of treatment is to identify and eliminate the underlying problem, if possible. If fleas or flea allergies are identified, the fleas must be controlled. Likewise, other parasites or allergies need to be addressed. We may need to do further tests (such as skin scrapings or blood tests) to help diagnose the true reason that the hot spot ocurred in the first place. Without treatment of the root of the problem, the hot spots are likely to recur.
- Cleaning. Sedation or full anesthesia may be needed to allow thorough clipping of the hair and cleaning of the hot spot with an antibacterial soap. This is the most basic aspect of treatment, since it allows the skin to breathe and removes a lot of the surface bacteria. This initial cleaning makes the dog vastly less itchy, sore, and uncomfortable.
- Drying agents. If the hot spot is particularly moist or weeping, a topical drying agent may need to be used. An example of this is aluminum acetate. It comes in powder form and should be made up (as directed on the package) into a solution. The solution is dabbed on the hotspot every 8 to 12 hours and allowed to air dry, until the lesion is no longer moist.
- Antibiotics. In most cases antibiotics are prescribed to help prevent infection from invading deeper in to tissues. Sometimes topical creams or ointments are helpful, but only products prescribed by a veterinarian should be used. There are times when applying anything to the surface of the hot spot might actually make it worse, so follow your veterinarian's instructions closely and avoid trying home remedies.
- Cortisone. Cortisone is used to decrease itching in some cases. It is definitely not appropriate for all dogs, but can be very useful to treat underlying problems like flea allergies or other allergies. Your veterinarian will determine whether cortisone is appropriate for your pet.
- Elizabethan collar. Since hot spots are caused by self-trauma, an Elizabethan or cone collar is generally required to stop the dog from biting himself. It is used for several days, until the dog is more comfortable and not painful or itchy.