December and sub-zero temperatures are not what one would normally associate with pleasurable swimming weather. However, at a recent working lunch, my bookkeeper Natalie informed us that she was swimming a marathon and was close to completing it. And the rest of us were extremely impressed.
It was with some interest then that I read about a case of allergic contact dermatitis after swimming pool exposure in the journal Pediatric Dermatology.
[Gui M, Johansen M, Reeder M. An uncommon cause of swimmer’s rash: Allergic contact dermatitis to persulfates in pools. Pedriatr Dermatol 2023; 40(6): 1091-1093.]
This happens to my child!
Yes, I must admit, we hear this often. Most often it is eczema that is aggravated by the drying effect of frequent water immersion in the pool or sea, combined with an irritant effect of sunscreens. Rarely, it is due to an aggravation of eczema with sun exposure. Very rarely, it is due to urticaria after exposure to water, so called aquagenic urticaria, a very disabling condition.
What was the case?
The case in question was a 7 year old boy who gave a 3 year history of a widespread itchy, spotty rash which occurred 1-2 hours after being exposed to waterparks, home pools and hot tubs. It didn’t occur after freshwater swimming, bathing or showering.
So what was the cause of the rash?
In order to keep swimming pools clean they need to be cleaned daily and undergo periodic “shock” treatments. These periodic “shock” treatments are used to get rid of organic contaminants and breakdown chloramines. Shock protocols can include either a chlorine or nonchlorine agent. Nonchlorine agents often include a chemical called potassium peroxymonopersulfate (PPMS).
What is PPMS?
PPMS is a persulfate and persulfates are strong oxidising agents. They are widely used as bleaching agents in all sorts of products from hair-bleaching products, the bleaching of flour for baking, but also in paper processing, electronic microchip processing, denture cleaning, water treatment and shock treatment of hot tubs and swimming pools. They can also be used in commercial livestock farming and aquamarine operations.
Persulfate exposure can cause an immediate-type allergic reaction as well as allergic contact dermatitis.
So what happened?
The boy was patch tested to ammonium persulfate, a commercially available patch testing agent with cross reactivity to PPMS and hence can be used as an alternative screening agent for PPMS allergy. The test was positive and he has had no further episodes of the dermatitis with avoidance of persulfates.
Is this common?
It may well be, but many of the cases in the literature are adult cases with a hand dermatitis in someone with occupational exposure to persulfates eg hairdressers, pool maintenance people, bakers and cleaners. However, as children don’t tend to do the above, generalised dermatitis after swimming pool or hot tub exposure is more common.
Hopefully, this will not put off those of you who are keen December swimmers (in the northern hemisphere, that is!)
Dr Sandy Flann, Consultant Dermatologist.