Pediatric dermatology: What's your Dx?


Multiple tender red papules on the trunk



Summertime, and a painful rash on the trunk:
What's your Dx?

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Choose article section...Diagnosis: Hot tub folliculitis

By Bernard A. Cohen, MD

One summer Monday morning, a healthy 11-year-old girl awoke to find a painful rash had erupted over her trunk. She had also developed a low-grade fever and told her mother that she was "just not feeling right." Her mother gave her a dose of ibuprofen and brought her to your office for evaluation.



On examination, the girl's body is marked by many tender red papules, some with central pustules. She is afebrile. No other family member has had a history of rash or recent febrile illness, and the family owns no pets. A possible clue: She celebrated her 11th birthday over the preceding weekend with a backyard pool party.

  • What is the diagnosis?

  • What other pertinent historical clues would help nail down the diagnosis?

  • How would you evaluate and treat this patient?

Diagnosis: Hot tub folliculitis

This girl's rash is a vivid example of hot tub folliculitis, which is an acute suppurative folliculitis caused by a gram-negative bacterial microorganism—most commonly Pseudomonas aeruginosa or another member of that genus. With hot tub folliculitis, pruritic or painful papules, papulopustules, nodules, and urticarial lesions typically appear on the trunk eight to 48 hours after exposure. The infection originates in contaminated artificial bodies of water such as whirlpools, swimming pools, spas, and hot tubs.1–4

Clinical features. The most prominent lesions develop on areas covered by bathing suits, where exposure is longest and irritation most persistent. Occasionally, the extremities are affected and painful violaceous nodules may develop on the palms and soles. Nodules on the palms and soles sometimes cause eruptions referred to as eccrine hidradenitis because the organisms enter the skin through the eccrine sweat ducts. The organism can be cultured from pustules and nodules as well as from contaminated pool water and filtration units.1–4

Although the rash may be an isolated finding, some affected people complain of fever, myalgias, arthralgias, and flu-like symptoms. In an outbreak of hot tub folliculitis at a hotel swimming pool in Maine in February 2000, several people also developed otitis externa from which Pseudomonas was cultured.2 (P aeruginosa is the most common cause of otitis externa.)

History. Gram-negative folliculitis usually occurs in mini-epidemics traced to exposure to contaminated water. In one report, 19 of 20 people who attended a birthday party at a hotel pool and hot tub in Colorado developed the dermatitis2; although none of the people became seriously ill, a rash persisted in many for as long as one week. Silverman and Nieland reported an outbreak in a family and their neighbor within two days of a hot tub party.1 A large outbreak was reported after people used a water slide in Utah: 265 of the 650 visitors to the park became infected on a single day.3

Treatment. Pseudomonas is exquisitely sensitive to drying, so other than avoiding the contaminated water source, treatment is unnecessary. Soaking in an acetic acid bath or applying benzoyl peroxide gel or wash, or another antiseptic and drying agent, may also clear up the eruption. Oral ciprofloxacin usually brings rapid improvement in patients who exhibit systemic symptoms.

Prevention. The best way to prevent gram-negative folliculitis is to maintain an adequate chlorine concentration and the correct pH level in hot tubs, whirlpools, and swimming pools. High temperature and heavy use lead to rapid breakdown of chlorine, making close monitoring of water quality by trained staff vital. Before a contaminated pool is allowed to reopen, it needs vigorous cleaning and disinfecting. Potentially contaminated bathing suits and towels should be treated by thorough laundering and drying before they are used again.

Differential diagnosis. Hot tub folliculitis is distinguishable from an insect bite because the latter is intensely pruritic and tends to occur on exposed sites. Gram-positive organisms usually cause chronic recurrent folliculitis, furuncles, and boils. Gram-positive organisms may be common in adolescents who shave their legs and in younger children who have diaper dermatitis, enuresis, and other conditions that irritate the buttocks and trunk.

Our patient's folliculitis cleared up in a week, without treatment. All the children who attended her party developed transient papules and pustules. For confirmation, P aeruginosa was grown from pus obtained from the central pustule of one of the nodules.


1. Silverman AR, Nieland ML: Hot tub folliculitis. A familial outbreak of Pseudomonas folliculitis. J Am Acad Dermatol 1983;8:153

2. Pseudomonas dermatitis/folliculitis associated with pools and hot tubs—Colorado and Maine 1999–2000. MMWR Morb Mortal Wkly Rep 2000;49:1087

3. An outbreak of Pseudomonas folliculitis associated with a waterslide—Utah. MMWR Morb Mortal Wkly Rep 1983;32:425

4. Bhatia A, Brodell RT: Hot tub folliculitis: Test the waters—and the patient—for Pseudomonas. Postgrad Med 1999;106:43


The next installment of Pediatric Dermatology: What's your Dx? will appear in October 2002

For this case and related images, or to contribute new images from your own cases, see Dr. Cohen's Web site at .


DR. COHEN, who serves as section editor for Pediatric Dermatology: What's your Dx?, is director, Pediatric Dermatology and Cutaneous Laser Center, and associate professor of pediatrics and dermatology at Johns Hopkins University School of Medicine, Baltimore. He is a contributing editor for Contemporary Pediatrics.


Pediatric dermatology: What's your Dx?. Contemporary Pediatrics 2002;7:39.

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