Mystery Rash in Runners

The Williams Cross Country running team went to a meet on the Connecticut shore on Saturday, October 28. There had been a big storm the previous day. The course took them through brackish water sometimes thigh deep. Within a 24 - 48 hours, around half of the runners had developed intensely pruritic lesions on arms and legs. The vast majority of the lesions were on exposed skin. The primary lesion appears to be a juicy papule or a clear vesicle. Some of these have crusted over in a few days. The lesions are discrete. They do not have the linear pattern characteristic of phytocontact dermatitis from a plant such as poison ivy. The pictures were taken of the legs of an 18 yo woman and a 21 yo man. The lesions were quite similar.




It's likely that this is from something dispersed in the brackish water they ran through. Runners from other schools were affected as well. About 50 runners from Williams College developed the eruption.

The possibilities include:
Atypical plant contact dermatitis (Some plant toxin such as urushiol churned up by the storm and floating in the water.)
Jellyfish nematocysts free floating after the storm and blown in
Bird schistosomes -- this is severe for that.
Bacterial infection (a culture was taken from one student and results were not specific)

Do you have other thoughts? What is your opinion?

Solution: The Cross Country course was redirected after the storm. A new path was cut though brush to circumvent a brackish area. It is likely that the new path went through poison ivy. The appearance of the rash 24 - 48 hours after exposure in the majority of runners and the quality of the itch suggests rhus contact dermatitis.