Young Girl with a Pruritic Rash

This 8-year-old girl came down with this itching rash following a horseback ride and a soak in a whirlpool spa. Other than itching, she has no symptoms and is in good health with no significant past medical history or medications.

What is your diagnosis?

1. Chiggers
2. Swimmer's itch
3. Flea bites
4. Sea bather’s eruption
5. Pseudomonas folliculitis

Diagnosis

This itching papular and pustular eruption, limited mostly to the bathing suit area following the use of a whirlpool spa, is classic for Pseudomonas folliculitis also known as hot tub folliculitis. It is caused by overgrowth of Pseudomonas when the antibacterial chemical levels in the water are too low.

Treatment is supportive for the patient as it is self-limited in most cases. Anti-Pseudomonal antibiotics including ciprofloxacin are only used in severe cases and fluoroquinolones are usually avoided in children. The spa should be cleaned and the chemical levels adjusted appropriately. Less commonly, Pseudomonas in hot tubs can cause tender erythematous nodules of the feet and hands known as “hot hand-foot syndrome.”

Chiggers can also present as erythematous itching lesions, sometimes with a pustular center. In contrast to this patient’s lesions being underneath her bathing suit, chigger infestations usually occur at areas where clothing stops the migration of the larva hence they often cluster at beltlines or the top of the socks.

Humans are not the usual host for fleas, but they will sometimes transfer from an infected host causing clusters of bites but in a more nondescript pattern especially on the lower extremities.²The bites are usually popular, sometimes with a central punctum, but not typically pustular.

In contrast to hot tub use, swimmer's itch, also called cercarial dermatitis, is usually contracted in freshwater due to the cercaria from schistosomes released by infected snails penetrating the epidermis. It causes a diffuse erythematous macular rash that progresses to a papular rash with itching for a week.

Seabather’s eruption also occurs in areas covered by bathing suits and causes macular or papular erythematous lesions, but as the name implies would be contracted in saltwater. It occurs in sporadic outbreaks and may be due to a larval infestation.

About the Author

Daniel Stulberg, MD, is a Professor of Family and Community Medicine at the University of New Mexico. After completing his training at the University of Michigan, he worked in private practice in rural Arizona before moving into full-time teaching. Stulberg has published multiple articles and presented at many national conferences regarding skin care and treatment. He continues to practice the full spectrum of family medicine with an emphasis on dermatology and procedures.