Hot tub chemical can cause pruritic rash

The next time you see a patient presenting with a widespread, severely pruritic rash, ask them if he or she has been in any hot tubs lately. A common chemical used in hot tubs called potassium peroxymonosulfate could be the culprit.

The rash tends to affect the back, calves and inner parts of arms.

Matthew Zirwas, M.D., of Ohio State University Medical Center, Columbus, Ohio, is a bit of a sleuth when it comes to getting to the source of mysterious allergens. He says allergy to the chemical is much more common than many dermatologists realize. Physicians can confirm the diagnosis with a patch test with ammonium persulfate.