Why do I get a rash after the beach?

The beach offers three different rashes, and the water versus sun split is the first clue. If you swam - especially in a lake, pond, or shallow shore water - think swimmer's itch: the CDC explains it as an allergic skin reaction to microscopic parasites released by infected snails into fresh and salt water. The parasites burrow into skin and die there, producing tingling and then small itchy red spots or blisters within hours, worst on skin the swimsuit did not cover. It is not contagious, needs no person-to-person precautions, and usually settles in a week or so - towelling off briskly right after swimming is the known prevention. If the rash appeared hours to days after sun on skin that does not usually see daylight - chest, arms, the V of your neck - think polymorphic light eruption, a common sun-sensitivity reaction the NHS describes: small raised spots or larger blotchy areas, itchy or burning, more common in spring and summer, settling on its own if you stay out of the sun, but tending to recur each sunny season. The third is simple irritation: heat, sweat, salt, sand, and a wet swimsuit rubbing for hours. Red flags: a rash with fever or feeling genuinely unwell, blistering over a large area, a rash that spreads beyond sun-or-water-exposed skin, or one that persists past two weeks - those get a GP look. Pymander is a free AI doctor, 24/7 by text, that can help you match your pattern.