In article ,
David in Normandy wrote:

My forearms are covered in horrible red blisters, like lots of burn
wounds, they are a real mess. ...

Nasty. You'll recover, but it will take a while.

I wish I knew exactly what type of weed did the damage. I know that
amongst the weeds there was one of those big plants that look like a
thistle but have yellow flowers, there were also lots of forget-me-nots
and some morning glory. I'm not aware of any of those having dangerous sap?

Don't be confused by the crap the gutter press puts out. There
are thousands of common plants that can cause that, and people
vary immensely in their responses. Things are nowhere near as
simple as poisonous/non-poisonous. All that you can tell is that
you are allergic to one of those plants, and it was probably a
photosensitivity, so wouldn't have happened on a really gloomy day.

It can be caused by grass, and then is associated with hay fever,
for example.


Regards,
Nick Maclaren.