Hot spots are red, moist, irritated patches of skin that appear suddenly on dogs, often spreading within hours. Veterinarians call them pyotraumatic dermatitis, and they’re one of the most common skin problems in dogs. The term “hot spot” also has a separate meaning in medical imaging, where it refers to areas of unusual activity on a bone scan or PET scan. Most people searching this term have a dog with an angry-looking sore, so let’s start there.
What a Hot Spot Looks Like on a Dog
A hot spot typically appears as a raw, wet, red patch of skin that may ooze pus or fluid. The area is often warm to the touch, which is where the name comes from. Hair around the sore may be matted or missing entirely, and the surrounding skin can look inflamed and swollen. Dogs will lick, chew, or scratch at the spot relentlessly because it’s intensely itchy and painful.
These lesions show up most often on the cheek, neck, and outer thigh. A study of 44 dogs with hot spots found a strong correlation between breed and where the sore developed, suggesting that body shape and coat type influence which areas are most vulnerable. Hot spots can go from a small irritated patch to a large, spreading wound in less than a day, which is why they tend to catch owners off guard.
Why Hot Spots Develop
A hot spot starts with anything that makes a dog scratch, lick, or chew at one area of skin. That repeated trauma breaks the skin’s surface barrier and lets bacteria in. The main culprit is a bacterium called Staphylococcus pseudintermedius, which normally lives harmlessly on a dog’s skin and mucous membranes. When the skin is damaged, this otherwise peaceful resident turns pathogenic and triggers a rapid, localized infection.
The initial trigger can be almost anything that causes itchiness or skin irritation:
- Flea allergy dermatitis: Even a single flea bite can set off an intense allergic reaction in sensitive dogs, leading to frantic scratching.
- Environmental or food allergies: Seasonal pollen, dust mites, or certain proteins in food are common culprits.
- Ear infections: Dogs with ear infections often scratch at the skin below and behind the ear, creating hot spots on the cheek and neck.
- Moisture trapped in the coat: Dogs who swim, wade, or get caught in rain are prone to hot spots if their thick coat doesn’t dry fully. Matted fur holds moisture against the skin, creating ideal conditions for bacterial growth.
- Anal gland problems: Infected or impacted anal glands cause dogs to lick and chew at their hindquarters, which can produce hot spots near the tail and thighs.
Once a hot spot forms, the cycle feeds itself. The infection causes more itching, which causes more scratching, which damages more skin, which lets the infection spread further. Without intervention, a small sore can expand dramatically in a matter of hours.
Which Dogs Are Most at Risk
Dogs with thick, dense, or double coats are especially prone because their fur traps heat and moisture close to the skin. Golden Retrievers, German Shepherds, Labrador Retrievers, and Saint Bernards are among the breeds most commonly affected. Hot spots peak in warm, humid months when dogs are more likely to swim or get wet and when flea populations are at their highest. Dogs with underlying allergies or recurring ear infections tend to get hot spots repeatedly.
How Hot Spots Are Treated
Treatment focuses on three things: stopping the infection, breaking the itch-scratch cycle, and identifying whatever triggered the problem in the first place. The area around the hot spot is typically clipped to remove matted, contaminated fur and allow air to reach the skin. The wound is then cleaned with an antiseptic solution. Your vet may prescribe a topical treatment to fight the bacterial infection and reduce inflammation, and in more severe cases, oral medications to control itching or clear deeper infection.
Most hot spots improve noticeably within a few days of treatment and heal fully within one to two weeks, as long as the dog stops traumatizing the area. An e-collar (the “cone of shame”) is often necessary to prevent licking and scratching while the skin heals. If the underlying trigger isn’t addressed, though, hot spots tend to come back.
Preventing Recurrence
Since hot spots are almost always secondary to something else, prevention means managing the root cause. Keeping your dog on consistent flea prevention year-round eliminates the most common trigger. If allergies are the issue, working with your vet to identify and manage them, whether through diet changes or allergy-specific treatment, makes a significant difference.
Grooming matters more than many owners realize. Regular brushing prevents mats that trap moisture. After swimming or baths, dry your dog thoroughly, paying special attention to the areas behind the ears, under the neck, and around the hindquarters. Dogs with very thick coats may benefit from a shorter trim during hot, humid months. Keeping ears clean and dry after water exposure helps prevent the ear infections that so often lead to hot spots on the face and neck.
Hot Spots in Medical Imaging
Outside of veterinary medicine, “hot spot” has a completely different meaning. In bone scans and PET scans, a hot spot is an area where a radioactive tracer accumulates more than expected, showing up as a bright spot on the image. This signals that something unusual is happening in that part of the body, whether increased bone metabolism, inflammation, or rapid cell growth.
On a bone scan, hot spots can indicate arthritis, fractures (including stress fractures too subtle for standard X-rays), bone infections, or cancerous tumors. Cancer cells multiply rapidly and stimulate increased bone repair activity, which draws more tracer to the area and makes it light up on the scan.
PET scans work similarly but use a sugar-based tracer. Because cancer cells consume glucose faster than normal cells, they absorb more of the tracer and appear as hot spots. Doctors measure the intensity of uptake using a standardized scale to help distinguish between concerning and benign findings. However, infections and inflammatory conditions can also produce bright spots on a PET scan, so a hot spot on any imaging study doesn’t automatically mean cancer. It means something in that location needs further investigation.