This is WHY this site exists! The poison ivy rash is awful, and it so easy to get and so easy to avoid. This fellow was just going fishing, wearing shorts, and there must have been some very ripe poison ivy or poison oak right along the shore, which we would guess is true MUCH of the time along streams.
The super nasty rash is on the left, the other two are his ankle in the process of getting more… or maybe in the process of getting worse!
With a bad one, it starts to itch the next day, but the ugly bubbles and scabs will take a week to form and several weeks to go away.
Go study what poison ivy looks like here, and California poison oak here, and Atlantic poison oak (!) here.