Dermadilemma# 2: What caused this rash in a 10-year-old girl?
A 10-year-old female presents to the clinic with complaints of an itchy rash on her buttocks for 2 days. Hydrocortisone cream and oral diphenhydramine have been ineffective. She denies a history of allergies, using new soaps, or detergents, but does note that she purchased a new bathing suit which she wore for the first time just prior to onset of the rash. There is no fever, chills or systemic symptoms, and the rash is only present on the buttocks. She has been vaccinated for Varicella virus. What is your diagnosis?

A: Contact dermatitis

B: Sea bather’s eruption

C: Hot tub folliculitis

D: Scabies

E: Herpes Zoster virus

Answer: C. Hot tub folliculitis. Hot tub folliculitis is generally a benign, self-limited condition caused by bathing in under-chlorinated pools and hot tubs contaminated with Pseudomonas aeruginosa. Papules, nodules, or pustules may occur and are generally itchy. Some patients will have a low-grade fever and malaise. Lesions may be anywhere on the body. Most cases will improve without treatment. Severe cases that are highly symptomatic or persistent may be treated with ciprofloxacin. Upon further questioning the girl had worn her new bathing suit in a hot tub the evening before the rash occurred. It was unknown if others in the hot tub had similar rashes. 

Sea bather’s eruption has a very similar appearance to hot tub folliculitis but requires a history of swimming in the ocean. Lesions occur strictly under a bathing suit, wet suit, or even watch band. This condition occurs when larvae of the Cnidaria phylum (jellyfish) release nematocysts and inject toxins. This condition is self-limited and should be treated by removing swim garments and rinsing the skin, topical steroids, and oral antihistamines. 

The appearance of this rash is dissimilar to scabies, as is the location. HZV would be unlikely in a 10-year-old and would not be on both buttocks. 

Hot tub folliculitis can be prevented by maintaining proper levels of chlorine and pH in bathing tubs and pools.