It often starts with nothing more than a dog paying a little too much attention to one patch of skin. By evening, the fur is wet and matted; by the next morning, there is a raw, red, oozing sore the size of your palm where healthy skin was a day before. Few canine skin problems appear as fast — or look as alarming — as a hot spot.
Veterinarians call it acute moist dermatitis or pyotraumatic dermatitis, and both names tell part of the story: it is sudden (acute), it is wet (moist), and it is largely self-inflicted (pyotraumatic — a bacterial infection driven by the trauma of the dog's own licking, chewing, and scratching). Hot spots are one of the most common reasons dogs visit the vet in summer, they are intensely painful, and they will keep coming back until the itch that started them is found and treated. Here is what the science says about why they happen, how they are treated, and how to keep your dog from getting the next one.
What a Hot Spot Actually Is
A hot spot is a localized area of skin inflammation and bacterial infection. It begins when something makes one patch of skin itch or hurt. The dog responds the only way it can — licking, chewing, and scratching — and that self-trauma damages the skin surface, letting the bacteria that normally live harmlessly on the skin (most often Staphylococcus pseudintermedius) multiply in the warm, moist, broken tissue. Infection makes the area even itchier and more painful, the dog attacks it harder, and the lesion expands. This itch-lick cycle is the engine of every hot spot, which is why the sores can grow dramatically within 24 to 48 hours.
A typical hot spot is a well-defined patch of red, moist, oozing skin with hair loss, often ringed by wet, matted fur that hides its true size. It may weep serum or pus, crust over at the edges, and give off a distinct odor. Common locations are telling: the cheek or the side of the face and neck (often linked to an underlying ear infection), and the hip or rump area (classically linked to fleas or anal gland problems). Hot spots are painful enough that even gentle, friendly dogs may flinch or snap when the area is touched — a warning worth remembering before you examine one at home.
What Triggers the Itch
The hot spot itself is the visible endpoint. The real question is what started the itching, and the list of common culprits is long:
- Fleas and flea allergy dermatitis — the single most commonly reported trigger. In an allergic dog, one flea bite can ignite an itch storm.
- Environmental or food allergies, which inflame the skin and lower the threshold for self-trauma.
- Moisture trapped in the coat after swimming, bathing, or rainy walks — especially in dense, double-coated fur that never fully dries.
- Ear infections, which drive scratching at the face and neck.
- Insect bites and stings, mites, and other parasites.
- Anal gland problems, which draw chewing at the rump and tail base.
- Matted or dirty coats that irritate the skin beneath.
- Boredom or stress licking, in dogs without a medical trigger.
Anything on this list can start the cycle — which is also why treating only the sore, without addressing the cause, is the classic recipe for a repeat performance a few weeks later.
Which Dogs Get Them Most
Any dog can develop a hot spot, but the condition is dramatically more common in thick- and double-coated breeds: Golden Retrievers, Labrador Retrievers, German Shepherds, Newfoundlands, Saint Bernards, and Rottweilers all appear repeatedly in the veterinary literature. Their dense undercoats trap heat and moisture against the skin, creating exactly the environment skin bacteria love. Dogs that swim frequently are at particular risk for the same reason.
Timing matters too. Hot spots can occur year-round, but case numbers climb sharply in warm, humid weather, when coats stay damp longer and fleas are most active. If your dog has had one hot spot, the odds of another are higher — usually because the underlying allergy or parasite problem is still there.
How Hot Spots Are Treated
Because hot spots are painful, infected, and often much larger than they look under the fur, a veterinary visit is the safest route for anything beyond a very small, superficial sore. Treatment follows a consistent logic:
- Clip the fur over and around the lesion. This reveals the full extent of the sore and lets air reach the skin — moisture and matted hair are what keep the infection going. Many dogs need sedation for this because the area is so painful.
- Clean the area gently with a chlorhexidine-based antiseptic.
- Control infection with topical medication; deeper or spreading infections may need oral antibiotics.
- Stop the itch — typically with a short course of a corticosteroid or an anti-itch medication such as oclacitinib (Apoquel). Breaking the itch is what breaks the cycle.
- Block self-trauma with an Elizabethan collar until the skin heals. This step is not optional; a dog that can still reach the sore will undo everything else.
- Find and treat the trigger — flea control, ear infection treatment, anal gland care, or an allergy workup. Skipping this step is why hot spots recur.
With proper treatment, most hot spots dry out and begin healing within a few days and resolve fully within one to two weeks. At home, resist the urge to reach for the human medicine cabinet: hydrogen peroxide stings and damages healing tissue, and many human ointments (and anything containing zinc) are unsafe if licked. If a sore is small, some owners can manage it with careful trimming, dilute antiseptic cleaning, and an e-collar — but if it is large, deep, spreading, multiplying, or not clearly improving within a day or two, or if your dog seems feverish or lethargic, see the vet.
Preventing the Next One
Prevention is mostly about removing the triggers before they start the cycle. Year-round flea and tick prevention is the single most effective step, given how often fleas are the spark. Dry your dog thoroughly after swimming or bathing — a towel may be enough for a short coat, but a double-coated dog may need brushing and a blow dryer to get moisture off the skin. Groom regularly to prevent mats, and consider a summer trim for very dense coats. Manage known allergies with your veterinarian rather than riding out each flare. And for dogs that lick out of boredom, more exercise, play, and mental enrichment address the behavior at its root.
The Bottom Line
A hot spot looks dramatic, and it genuinely hurts — but it is one of the more fixable problems in veterinary dermatology. The sore itself responds quickly to clipping, cleaning, and anti-itch treatment. The real work is upstream: finding the flea, the damp undercoat, the ear infection, or the allergy that lit the fuse. Treat the cause along with the sore, keep the coat clean and dry, and stay ruthless about parasite prevention, and most dogs never need to go through it twice.