What Are Hot Spots on Dogs?

Hot spots are one of the most common skin conditions in dogs and can develop literally overnight. A dog goes to bed with normal skin and wakes up with a raw, oozing, painful lesion that may be several inches across. They're technically called "acute moist dermatitis" — and the name describes them well: they're acute (sudden), moist (oozing serum and sometimes pus), and dermatitis (skin inflammation).

The mechanism: something causes initial itching or irritation (a flea bite, allergic reaction, minor scratch, moisture trapped under the coat). The dog responds by licking, chewing, or scratching. This damages the skin, creating a warm, moist environment perfect for bacterial growth. Bacteria multiply, causing more itching, which causes more self-trauma, which causes more infection — a vicious cycle that can enlarge a hot spot from a small patch to a dinner-plate-sized lesion in hours.

Common triggers: flea bites (the #1 trigger), allergies (environmental or food), ear infections (causing head/neck scratching), anal gland problems (causing rear-end licking), insect bites, contact irritation, moisture trapped under thick fur, matted hair, and boredom/stress grooming.

Hot spots are most common in warm, humid weather and in breeds with thick double coats. The chest, hip, and head (near the ears) are the most common locations.

Treatment requires breaking the itch-scratch cycle: the area is clipped free of hair, cleaned, and treated with antibiotics (topical and sometimes oral). Anti-itch medication (corticosteroids or apoquel) stops the self-trauma. An Elizabethan collar prevents the dog from reaching the lesion. With proper treatment, hot spots heal in 5-7 days. Without treatment, they can spread and deepen into a serious infection.