Hot Tub Folliculitis

Hot tub folliculitis (Pseudomonas folliculitis) is a self limiting follicular infection with Pseudomonas aeruginosa acquired from contaminated warm water in hot tubs, whirlpools, swimming pools, water slides and loofahs. Infection follows 8 hours to 5 days after exposure.

• Occurs when chlorine is low (under 1 ppm) or pH is outside 7.2 to 7.8.
• Occlusion of skin by wet swimwear in the water favours infection.

Itchy or tender erythematous follicular papules, pustules and nodules mainly on the trunk, buttocks, axillae and hips, sparing the face, palms and soles.

• May be accompanied by malaise, low grade fever, headache, sore throat, otitis externa and painful breast swelling.
• Lesions resolve over 7 to 14 days, sometimes leaving hyperpigmentation.
• Differential diagnosis: staphylococcal folliculitis, miliaria, acne vulgaris, Malassezia folliculitis, eosinophilic folliculitis, scabies, swimmer itch (cercarial dermatitis), insect bites, contact dermatitis, varicella.
• Complications: cellulitis, abscess, mastitis, otitis externa, urinary tract infection, sepsis in immunocompromised or neutropenic patients, post inflammatory hyperpigmentation.

Clinical, with history of recent water exposure and cluster cases.

• Swab or biopsy culture of pustule for Pseudomonas in severe or atypical cases, and of the water source.
• Blood cultures and full blood count when febrile or immunosuppressed.

Most resolve without antibiotics, so give supportive care and treat only complicated disease.

• Supportive: cool compresses with acetic acid 2 percent (diluted white vinegar), loose cotton clothing, analgesia with paracetamol 1 g up to four times daily, calamine or emollient for itch, avoid shaving, wash swimwear after each use and do not reuse.
• Pharmacological: oral antihistamine for itch (cetirizine 10 mg at night); topical gentamicin 0.1 percent cream twice daily for 7 days for localised persistent lesions; ciprofloxacin 500 mg twice daily for 7 days for severe, extensive or persistent disease and for immunosuppressed adults; ceftazidime 1 to 2 g IV every 8 hours for systemic Pseudomonas infection in neutropenia or immunosuppression.
• Procedures: drainage of abscess; remove infected source.
• Special groups: pregnancy, avoid ciprofloxacin and use supportive care; children, avoid fluoroquinolones and use topical care, referral if severe; immunosuppressed or diabetic, early systemic therapy; HIV, treat promptly.
• Red flags: fever above 38 degrees Celsius, deep abscess, rapid spread, mastitis, neutropenia, immunosuppression, sepsis.
• Follow-up: review at 1 week if on treatment; notify the pool or spa operator for water treatment (free chlorine 1 to 3 ppm, pH 7.2 to 7.8); reassure about recovery.