CONDITION

Acute Moist Dermatitis (Hot Spots)

Why this matters now

Hot spots often develop rapidly, sometimes appearing within hours. They occur most frequently in warm, humid weather when conditions favour bacterial growth and when underlying allergies may flare. Double-coated breeds and dogs with thick fur are particularly prone, especially after swimming, bathing, or rain exposure.

These lesions typically begin as a small area of irritation that the dog licks or scratches. The combination of moisture, bacteria, and self-trauma creates a rapidly expanding wound. Without intervention, a small spot can become a large, painful lesion within 24 to 48 hours. Secondary deeper infection can occasionally develop if the condition is not addressed.

Signals & patterns

Early signals

Sudden intense licking or scratching at one spot

Dogs may focus obsessively on a specific area, often detected by hearing repeated licking sounds.

Small area of moist, reddened skin

Early lesions appear as wet, inflamed patches, sometimes hidden beneath matted fur.

Localised pain on touch

The affected area may be tender, causing the dog to flinch or turn when approached.

Matted fur with discharge

Hair over the lesion often becomes stuck together with serum or pus.

Later signals

Rapidly expanding raw, oozing area

The lesion may grow substantially in size within hours, with clearly defined borders of hairless, inflamed skin.

Thick yellowish discharge or crusting

Bacterial colonisation produces purulent exudate that mats into surrounding fur.

Unpleasant odour from the lesion

Bacterial activity often creates a distinctive smell from affected areas.

Click to read about the biological mechanisms

How this is usually investigated

Diagnosis is usually apparent from the characteristic appearance. Investigation often focuses on identifying underlying triggers to prevent recurrence.

Physical examination

Purpose: To assess the lesion size, depth, and identify any underlying cause
Considerations: The area beneath matted fur often reveals a larger lesion than initially apparent. Checking for flea evidence, ear infections, or matting is typically included.

Cytology of discharge

Purpose: To examine bacteria and cell types present
Considerations: Can help guide antimicrobial selection and identify any unusual organisms.

Assessment for underlying allergies

Purpose: To investigate if allergic skin disease is predisposing to hot spots
Considerations: May be considered if lesions recur, as flea allergy, environmental allergy, or food allergy often underlie repeated episodes.

Examination of ears and anal glands

Purpose: To check for local sources of irritation that may trigger scratching
Considerations: Ear infections and anal gland issues commonly provoke head and rear-end scratching that can initiate hot spots in those regions.

Options & trade-offs

Management aims to break the itch-scratch cycle, clear infection, and identify triggers. Various approaches may be combined depending on severity.

Clipping and cleaning the lesion

Removing hair from around the lesion and cleaning with appropriate solutions allows air exposure and removal of debris.

Trade-offs: May require sedation if the area is very painful. Essential for allowing the lesion to dry and heal.

Topical therapy

Antimicrobial and anti-inflammatory preparations applied directly to the lesion.

Trade-offs: Requires keeping the area accessible and may need frequent application. Effectiveness depends on preventing the dog from licking.

Systemic medications

Oral antibiotics and anti-inflammatory medications when lesions are severe or multiple.

Trade-offs: More practical for extensive lesions or when topical treatment alone is insufficient. Course length varies depending on response.

Preventing self-trauma

Elizabethan collars or protective clothing to stop licking and scratching.

Trade-offs: Essential for allowing healing but may cause temporary stress. Various collar styles offer different levels of comfort and restriction.

Addressing underlying triggers

Managing allergies, treating ear infections, or regular grooming to prevent matting.

Trade-offs: Long-term prevention depends on identifying and controlling underlying causes. May require ongoing management.

Common misconceptions

Misconception:

"Hot spots are caused by poor hygiene"

Reality:

These lesions develop from underlying irritation triggers, not uncleanliness. They involve normal skin bacteria that proliferate when conditions allow.

Misconception:

"They will dry out and heal on their own"

Reality:

The self-perpetuating cycle of itch and trauma typically causes rapid worsening. Breaking this cycle usually requires intervention.

Misconception:

"Shaving the fur will make it worse"

Reality:

Clipping away hair is generally an important part of management, allowing the lesion to dry and enabling topical treatment. The temporary cosmetic change supports healing.

If hot spots recur, noting patterns such as seasonality, association with swimming, or body location may help identify triggers. Monitoring for signs of underlying allergies, ear problems, or areas where fur becomes easily matted can guide prevention efforts. Regular grooming and prompt attention to any excessive licking or scratching may help catch new lesions early.

Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS