This is likely poison ivy, which is a Type IV (delayed) hypersensitivity mediated by T-cells. [FA2020 p112]
Notes to point to poison ivy: itchy linear vesicles (as the leaf touched), camping trip, on the extremities which would likely be exposed
Delayed type hypersensitivity helpful hint: the rash did not appear until a few days after he had returned from camping (5 days ago camping, 2 day history of rash)
flapjacksJust some additional information since this has come up for me before:
Poison ivy rash is caused by an allergic reaction to an oily resin called urushiol (Rhus dermatitis)+3
submitted by โcassdawg(1780)
This is likely poison ivy, which is a Type IV (delayed) hypersensitivity mediated by T-cells. [FA2020 p112]
Notes to point to poison ivy: itchy linear vesicles (as the leaf touched), camping trip, on the extremities which would likely be exposed
Delayed type hypersensitivity helpful hint: the rash did not appear until a few days after he had returned from camping (5 days ago camping, 2 day history of rash)