Seabather's eruption

Seabather's eruption is an itching dermatitis caused by a hypersensitivity reaction to the immature nematocysts of larval-stage thimble jellyfish (Linuche unguiculata), sea anemones (Edwardsiella lineata) and other larval cnidarians. The eruption is sometimes attributed to "sea lice" or "sea ants", but sea lice (Caligidae) are crustacean parasites of fish only.

It should not be confused with swimmer's itch.