I wondered about hogweed - I've come into contact with it once and it was nasty.
Blisters looked less blistery than mrs wows, and I had wierd purply bruising.
Needed mega-strength anti-histamine pills.
Since then, I've started reacting to bee and wasp stings. No idea if that has been caused by the hogweed or the antihistamines. there are suggestions that getting hogweeded once can leave you sensitive.