Giant Hogweed

Had a little blistery rash on the back of my hand for a few days that I couldn't place. Non of the usual 3 suspects eczema, sunburn, stinging nettles. 
Mentally traced back to a river side run with lots of hopping over vegetation because everything had suddenly grown. There's a few known patches of Giant Hogweed that SISI are working hard to get rid of. 
But took a wander tonight to check where I think I'd brushed against some and yep. There it is. 
Someone's already reported that stretch because its already been treated. Found a new bit as well so hopefully that will get dealt with soon. 
Generally against chemically killing plants but for Giant Hogweed in places people go I'm OK with it. It's nasty stuff. 

Extra: some little Giant Hogweed before it's grown up