What causes hot spots (moist dermatitis) in dogs?

Hot spots (also called acute moist dermatitis) are localized, inflamed, infected areas of skin that develop rapidly—often within hours. They’re usually the result of a self-reinforcing itch–scratch–infection cycle.

1. Underlying itch triggers (primary causes)

These are the most common starting points:

• Flea infestations
  Even a single flea bite can trigger intense itching, especially in dogs with flea allergy dermatitis.
• Allergies
  • Environmental (pollen, dust mites, mold)
  • Food allergies (proteins like chicken, beef, dairy)
• Parasites
  • Mites (e.g., mange)
  • Lice or ticks

👉 These conditions cause pruritus (itching) → dog scratches/licks → skin barrier breaks → bacteria invade.

2. Moisture + skin environment issues

Hot spots thrive in warm, damp conditions:

• Wet fur (after swimming, bathing, or rain)
• Poor grooming / matted coats
• Thick double coats (e.g., Golden Retrievers, Huskies)

Moisture traps heat and bacteria, accelerating infection.

3. Skin trauma or irritation

Anything that irritates the skin can trigger licking:

• Cuts, abrasions, insect bites
• Grooming irritation (clipper burn)
• Foreign objects (grass awns, splinters)

4. Behavioral factors

• Stress or anxiety
• Boredom-induced licking (psychogenic licking)

This is especially common in high-energy or under-stimulated dogs.

5. Ear or gland issues

• Ear infections → scratching around head/neck → hot spots nearby
• Anal gland problems → licking base of tail → hot spots in that area

6. Secondary bacterial infection

Once the skin is damaged:

• Bacteria (commonly Staphylococcus pseudintermedius) proliferate
• Leads to redness, oozing, odor, and rapid expansion of the lesion