Hot spots on dogs: what they are and why they keep coming back

One minute your dog seems fine; a few hours later there's a red, wet, angry patch of skin — often on the cheek, neck or hip — that your dog won't leave alone. That's a hot spot, known medically as acute moist dermatitis, and it can develop frighteningly fast. The good news: hot spots are very treatable. The important part: a hot spot is a symptom, and the dogs that get them again and again are almost always telling you about an underlying allergy.

Here's what hot spots are, what sets them off, how they're treated, and how to stop the cycle of repeats.

What a hot spot actually is

A hot spot is a small area of skin that becomes rapidly inflamed and infected because the dog has traumatised it themselves. As MedVet dermatologist Dr. Lauren Pinchbeck describes it, a hot spot involves a rapid increase of bacteria on the skin surface that is worsened by self-trauma to the area.

The loop is brutally fast: something itches → the dog licks, scratches or chews → that breaks the skin and traps moisture → bacteria multiply → it itches and hurts even more → the dog goes at it harder. Within hours you can have a raw, weeping, painful lesion. Hot spots are also more common in warm, humid weather and in thick- or long-coated dogs, where moisture sits against the skin.

What makes a dog itch in the first place

A hot spot doesn't appear out of nowhere — something starts the itch. The usual triggers:

• Flea allergy — the most common trigger of all. The Merck Veterinary Manual notes pruritus from flea allergy dermatitis is moderate to severe and the resulting licking, scratching and chewing can lead straight to acute moist dermatitis.
• Environmental allergy (atopic dermatitis) — pollen, dust mites, mould.
• Food allergy — an ingredient the dog reacts to.
• Ear infections and anal gland problems — dogs traumatise the skin near an itchy ear or rear.
• Trapped moisture or matting — after swimming or bathing, or under matted fur.
• A local irritant, sting, or something stuck in the coat.

Notice how many of those are allergies. That's the key to the recurring ones.

How hot spots are treated

Hot spots usually need veterinary treatment — they're painful, and they don't reliably clear on their own. Typical steps:

1. Clip and clean — the fur over and around the spot is clipped (often well beyond the visible edge) and the skin gently cleaned with a mild antiseptic so it can dry and breathe.
2. Treat the infection and inflammation — your vet may prescribe topical or oral medication to clear the bacterial infection and calm the itch and pain.
3. Stop the self-trauma — a temporary cone or a light cover prevents further licking while it heals.
4. Find and treat the trigger — flea control, ear treatment, or an allergy work-up so it doesn't simply come back.

Why yours keeps coming back

A one-off hot spot after a swim is one thing. But if your dog gets them repeatedly — or in the same spots, season after season — the hot spot is just the visible tip of an ongoing allergy. As Dr. Pinchbeck advises:

If food allergy is part of the picture, the triggers are the everyday proteins — and a hot spot is one more reason to investigate the diet rather than just patch the skin:

The path forward depends on the trigger: rock-solid flea control for flea allergy, an allergy work-up for atopy, and — if food is suspected — an elimination diet trial. As Tufts' Dr. Lisa Freeman stresses, that trial only works if you control everything your dog eats. (Not sure whether it's food or environment? See food vs. environmental allergies.)