Solved ID please.

Could anyone please tell me what this is. It's just on it's own growing on the allotment. Thanks in advance

 

Thanks @JWK I'll get it out. I don't need any more invasions

 

It affects some people worse than others. If I lift an armful of weeds with them in to a compost heap, shortly afterwards I'll have wet, red, sore spots all over the skin on the inside of my arms that'll last for weeks.

 

I found it reacts with sunlight to cause burns.
Not sure its a problem without exposure to sunlight.

 

So not likely to be a problem to those gardeners who do their weeding at night and subsequently don't go out during the daytime.

 

I think the issue is the sap destroys Melanin our natural protection from the sun. Once destroyed the sun can do it’s worst, ie it is not the sap that burns but allows the sun to burn. I am no expert so happy to be told l’m wrong

 

Yep, I think you summed it up there.

 

You can send it to me! I tried to start milkweed from seed several times and failed. It attracts our monarch butterflies