Help! My dog has acute moist dermatitis! Actually, it's just a hot spot.
With the weather warming up, our snowy days are turning to rainy wet ones. That's great! Bring on Spring!
However, with the warmer wet weather, comes something that drives a double-coated breed owner up the wall: hot spots.
Acute moist dermatitis ("hot spot") is a common skin ailment. These start with a small focal area of erythema [(from the Greek erythros, meaning red) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries] and pruritus (severe itching). The skin surface becomes moist and the hair often mats over the lesion, aggravating the condition. Predisposing factors include hot weather, humidity, sand, salt water, irritant chemicals (including greasy topical medications) and dips, patient compliance (is it a licker?) and a matted, unkempt hair-coat (Briggs, 1988).
Initial appearance of hot spot - wet, scabby areas.
These infections can occur from the skin becoming a perfect growth environment for fungal or bacterial growth, for example with the bacteria staphylococcus, which is a normally occurring bacteria found on healthy skin. However, when the skin becomes a moist, warm, growth environment this bacteria can bloom into a full infection, especially when protected by a thick double coat. This can also lead to cellulitis. Cellulitis is an infection of the deeper layers of skin and causes skin redness and swelling on the surface of your skin. Sores (ulcers) or areas of oozing discharge may develop, too.
How can we prevent this? Regular grooming, using a comb and slicker brush to ensure that all undercoat is removed and the skin has good airflow through the coarse guard hairs is pivotal. Also, after bathing be sure that the coat is fully dried, either with towels or forced air dryers (these are great for loosening undercoat as well to ensure the maximum amount of hair is removed). This is a time consuming process, but very important to ensure that moisture is not trapped and allowed to encourage bacterial growth. Remember, we are always covered in our own micro-environment of naturally occurring bacteria (waiting for an opportunity to grow).
There are times of the year where hot spots are more likely to occur as well, such as Spring and Summer, especially during periods of hot weather and high relative humidity. A coat that gets rained on and stays wet (often the undercoat is wet when the top coat looks dry) can also cause a problem and lead to fungal growth. The equivalent in horses is known as 'rain scald'. Hot spots are not necessarily a sign of mismanagement either, sometimes the animal can be predisposed due to compromised immunity and therefore more likely to be susceptible.
Should your dog develop a hot spot, the best first course of action is to clean the area with an antiseptic solution (bacti-stat or chlorahexadine), remove hair or debris that may be encouraging growth/protection of the bacteria/fungus, and treat topically with an antibiotic. Ensure the area is kept dry. You may have to scissor or clip hair away from the affected area. When using grooming tools, be sure to clean with a bleach solution afterwards to prevent spreading of the infection.
Your best bet is to ring your veterinarian for a recommendation, and probably an appointment. Topical or oral antibiotics may be prescribed, possibly the use of steroids if the infection warrants their use.
(left) hot spot after being debrided - note cellulitis and angry skin discolouration
(right) hot spot following 3 days of antibiotics - note reduction in discolouration and swelling and overall drier appearance
OM Briggs - Journal of the South African Veterinary Association, 1988 - journals.co.za
**Thank you Shelagh for the images