Hot Spots (Acute Moist Dermatitis)

Hot spots (pyotraumatic dermatitis or acute moist dermatitis) are rapidly developing, painful skin lesions caused by a cycle of irritation and self-trauma. A dog itches or licks a specific area - triggered by a fleabite, insect sting, ear infection, anal gland discomfort, contact irritant, or psychological stress - and the repeated licking or chewing creates a warm, moist environment where surface bacteria proliferate rapidly.

The result is a wet, matted, often malodorous lesion that appears to develop overnight and expands quickly. The dog continues to traumatise the area because it's itchy and painful, which makes it worse.

Hot spots can develop in any breed but are particularly common in dogs with thick, dense undercoats - Golden Retrievers, Labrador Retrievers, German Shepherds, St Bernards - where moisture is trapped against the skin.

Recognising a hot spot

• Acute onset: The lesion appears suddenly, often within hours
• Wet surface: Exuding serum or pus; the skin surface appears moist and glistening
• Hair loss over the lesion: The fur may be matted down or absent
• Well-defined border: Hot spots typically have a clear edge between the lesion and normal skin
• Redness and swelling: The underlying skin is inflamed and often warm to touch
• Pain: The dog will typically react to touching the area
• Dog interference: Constant licking, chewing, or scratching at the site

They most commonly occur around the head and neck (often linked to ear infections or fleabites), rump and base of tail (often linked to anal gland irritation or flea allergy), and hips (often moisture-related in thick-coated breeds).

Daily monitoring

Hot spots can expand rapidly - what was 2cm in the morning may be 8cm by evening if untreated.

Log daily:

• Size of the lesion (measure with a ruler or photograph with a reference object)
• Appearance: improving, stable, or worsening
• Whether the dog is being prevented from accessing the area (collar)
• Signs of the dog breaking through any preventive measure
• Signs of resolution: dry surface, hair regrowth at the margin

Treatment

Treatment is focused on stopping the self-trauma cycle, reducing the bacterial load, and managing the underlying trigger:

Clipping the hair: The area around the hot spot must be clipped to allow air circulation and allow topical treatment to reach the skin surface. This is important - treating through matted wet fur is ineffective.

Cleaning: Gentle cleaning with dilute chlorhexidine solution removes exudate and reduces bacterial load.

Topical treatment: Topical corticosteroid and antibiotic sprays or creams reduce inflammation and treat surface bacteria.

Systemic treatment: For significant or rapidly expanding hot spots, a short course of oral antibiotics and anti-inflammatory medication (prednisolone) gives faster, more reliable results than topical treatment alone.

E-collar (Elizabethan collar): Essential. The hot spot will not heal if the dog can continue to traumatise it. An appropriately fitted collar that prevents access to the lesion is non-negotiable.

Addressing the trigger: Without identifying and managing the underlying cause, hot spots will recur. Common triggers to investigate: flea allergy (has flea prevention been applied? is it current?), ear infection, anal gland irritation, environmental allergy, or psychological stress.

When to contact your vet

Contact your vet soon if:

• A hot spot has appeared and you cannot manage the dog's access to it
• The lesion is large (>5cm), rapidly expanding, or deeply infected
• Your dog is in significant distress

Contact your vet for a routine appointment if:

• Hot spots recur regularly - investigate the underlying trigger

A same-day call is appropriate for a large, rapidly developing lesion. Small, early lesions in dogs with a known hot spot history may be managed with a prescribed product your vet has provided for home use.

Frequently Asked Questions

Can I treat a hot spot at home? Small, early hot spots in dogs with a history of them may respond to home treatment - clipping the area, cleaning, and applying a prescribed topical product. But vet assessment is appropriate for any new or large lesion to confirm the diagnosis, clip adequately, and ensure the right treatment is used.

Why does my dog keep getting hot spots? Recurring hot spots almost always have an underlying trigger. Flea allergy is the most common cause in the UK - even one fleabite triggers intense itching in a sensitised dog, and a single flea can be very hard to find. Environmental allergies, food allergies, ear infections, and anal gland issues are other common recurring triggers. Investigate the trigger rather than just treating each episode.

My dog had a hot spot that seemed to heal but now there's one next door to it. What's happening? Satellite lesions adjacent to a healing hot spot can represent spread of the infection, incomplete treatment, or the dog finding a way to traumatise the area near the original lesion. Return to your vet for reassessment.

How long does a hot spot take to heal? With appropriate treatment and strict prevention of self-trauma, most hot spots are significantly improved within 3–5 days. Complete healing typically takes 1–2 weeks. If a lesion isn't showing clear improvement within a week of treatment, reassessment is needed.

Can I use human hydrocortisone cream on a hot spot? Not recommended without veterinary guidance. Human topical corticosteroids vary in strength, and some contain ingredients not suitable for dogs. Veterinary topical preparations are formulated appropriately and often combine an antibiotic with the anti-inflammatory.