Some lavender essential oil on it if you have any, and then put as much wet clay as you have and the person should not move around (spreads the poison), rest and drink lots of cooling fluids.
Benedryl or antihistamines may help too.
DH is very allergic to stings. The sooner you put the clay, the better. I keep a bown of wet clay in the cupboard at all times, best thing for burns after soaking in cold/icy water until pain diminishes (plus lavender oil).
If you (or anyone) wants to know about clay use (source, how to mix/store/use) lemme know.
Thanks lj and all those that responded.
Do you make your own clay?
When I was a kid, a friend and I would go dig clay out of creek for a lady we knew. She would eat it. I have no idea why.