What causes hot spots on dogs?

Hot spots—also called pyotraumatic dermatitis—are one of the skin problems I see most often in clinic, and they tend to alarm owners because they appear quickly and look painful. Knowing what most commonly causes them and what you can do at home right away helps your dog feel better faster and can prevent repeat episodes.

Why understanding hot spots matters to every dog owner

Most dog owners search for “hot spot” after finding a raw, wet patch of skin their dog is licking or chewing nonstop. In my experience those urgent searches are driven by three immediate goals: relieve the dog’s pain, stop the behavior that’s making the wound worse, and figure out whether the problem requires a vet. Hot spots are not just cosmetically unpleasant; they interfere with sleep, make grooming difficult, and can set a dog up for deeper skin infections that require antibiotics or other treatments.

Because these lesions usually progress quickly—sometimes within a day—owners who act early can often limit the size and depth of the wound. And because many hot spots are linked to preventable triggers, learning the typical causes pays off in reduced stress for both dog and owner and fewer interrupted walks, baths, or grooming sessions.

The main culprits behind hot spots

A handful of overlapping factors explain most hot spots and point to the right first steps: underlying allergies (which may be due to fleas, food, or the environment) often cause intense itching that leads dogs to scratch or lick; that self-trauma breaks the skin and creates a site for opportunistic bacteria or yeast to overgrow; trapped moisture or a matted coat can amplify irritation and hold bacteria against the skin; and simple behavioral habits—such as obsessive licking—can turn a small sore into a much larger lesion. In practice I typically see more than one of these factors at play in a single patient.

Inside the skin: how hot spots form

The process starts with a breach in the skin’s barrier. That breach may be microscopic—an irritated hair follicle from scratching—or more obvious, like a scrape. Local inflammation follows, and the dog’s response (scratching, biting, licking) perpetuates the damage. This is the classic itch–scratch–lick cycle: each action removes protective skin layers, increases local inflammation, and transfers mouth or environmental bacteria into the wound.

Once bacteria such as staphylococcal organisms are introduced, they often multiply on the warm, moist skin and can produce enzymes and toxins that further damage tissue. The lesion can become wet and oozing, with a foul smell in more advanced cases. That exudation prevents normal healing and may lead to rapid expansion of the affected area—you can sometimes watch a spot double in size over a matter of hours if the behavior isn’t controlled.

Because dogs’ mouths and skin both harbor microbes, secondary infection is common rather than rare. The combination of ongoing self-trauma and bacterial overgrowth tends to convert a simple irritation into an inflamed, painful wound that benefits from topical and sometimes systemic therapy. Understanding the cycle explains why stopping the behavior and cleaning the area are as important as treating infection.

Timing and triggers — when hot spots typically appear

Hot spots are more likely in warm, humid weather because moisture and heat create a bacterial-friendly environment. I see seasonal spikes in summer months, particularly in dogs that swim or roll in damp grass. Any recent bath, swim, or heavy perspiration—especially if the coat isn’t dried thoroughly—can be a trigger.

Long-haired or poorly groomed dogs are at higher risk because matted fur traps dirt and moisture next to the skin, reducing airflow. Dogs going through allergy flares—whether from fleas, pollen, or food—are also at greater risk because their skin is already itchy. Finally, dogs with repetitive behaviors, such as compulsive licking or redirected chewing after being unable to reach fleas elsewhere, often develop hot spots in predictable spots like the hips, base of the tail, neck, or limbs.

Warning signs and when to call the vet

Not every hot spot can be managed at home. Seek veterinary attention promptly if a lesion is expanding quickly or looks intensely painful, or if your dog has a fever, seems lethargic, or loses appetite. Strong foul odor, pus discharge, or continuous bleeding are signs that the infection may be more advanced and that systemic antibiotics or more intensive wound care might be needed.

Recurrent hot spots—multiple episodes in the same dog over weeks or months—may suggest an underlying problem such as uncontrolled allergies, fleas, a hormonal disorder, or a behavioral issue that needs targeted treatment. If a spot doesn’t improve after a few days of careful home first aid, or if multiple areas appear, that’s another reason to have your veterinarian evaluate the situation.

Immediate steps owners can take before reaching a veterinarian

The safest first steps are aimed at stopping self-trauma, reducing contamination, and getting you and your vet the best information. Clip the hair around the lesion to allow air to reach the skin and to give you room to clean it; when clipped the size and depth of the sore become clearer, and medicated treatments can be applied more effectively. I recommend using blunt-tip scissors or electric clippers and moving slowly—if the dog is uncomfortable, consider asking a helper to calm or gently hold them.

Clean the area gently with saline or a mild antiseptic solution that your veterinarian approves—diluted chlorhexidine or povidone-iodine are commonly used under guidance. Avoid harsh chemicals like undiluted hydrogen peroxide or alcohol on a raw wound because they can delay healing. After cleaning, keep the dog from licking the spot; an Elizabethan collar or a recovery suit usually works well until the lesion is less painful and less tempting.

Contact your veterinarian after those steps so they can advise on whether a topical prescription, oral antibiotics, or anti-inflammatory medication is necessary. If your dog is in severe pain, or if the lesion is large and smelly, plan to have it seen within 24 hours rather than waiting several days.

Reduce risk: home care and training strategies to prevent hot spots

Long-term prevention focuses on addressing the triggers and the behavior. Regular grooming to prevent mats, prompt drying after swimming or bathing, and routine checks of problem-prone areas reduce the chances that moisture and debris will initiate irritation. I encourage owners to establish a grooming routine appropriate to their dog’s coat type, and to learn basic clipping so small mats don’t become big problems.

Consistent flea and tick control is a high-yield prevention step; even a small flea burden can lead to intense itching and subsequent hot spots. For dogs with suspected food or environmental allergies, working with your vet on diet trials, elimination diets, or allergy testing can reduce flare frequency. Behaviorally, redirective training and enrichment reduce boredom or anxiety-driven licking. Simple changes—more walks, puzzle feeders, or supervised chew items—can make a real difference for dogs who lick when understimulated.

Tools and products that help manage hot spots

A few practical tools make both first aid and prevention easier. An Elizabethan collar or soft recovery suit is essential to break the lick–scratch–lick cycle while a wound heals. For owners more comfortable with hands-on care, a pair of electric clippers with a guarded blade and blunt-tip scissors helps safely remove surrounding hair. Keep a veterinarian-approved antiseptic shampoo or wipes on hand for routine cleaning after swims or outdoor activity.

Medicated shampoos containing chlorhexidine and antifungal agents may be prescribed for dogs with recurrent issues, and veterinary-strength flea and tick preventives are worth the investment for dogs that go outdoors frequently. If your dog is prone to obsessive licking, consider enrichment toys or puzzle feeders and consult a behavior consultant or trainer for strategies to interrupt the habit before it produces skin damage.

References and further reading

• Merck Veterinary Manual: “Pyotraumatic dermatitis (hot spots)” — https://www.merckvetmanual.com/ (search for pyotraumatic dermatitis)
• American College of Veterinary Dermatology: “Client Information Sheet — Pyotraumatic Dermatitis (Hot Spots)” — ACVD.org client resources
• American Veterinary Medical Association: “Skin Conditions — Pyotraumatic Dermatitis” — AVMA.org educational articles
• Journal of Veterinary Dermatology: review articles on canine pyoderma and the role of Staphylococcus spp. in skin infections
• Merck Veterinary Manual: “Canine Atopic Dermatitis” — for background on allergy-driven itching and management