On 09/05/2011 14:15, wrote:
In ,
Martin wrote:

Photosensitising by (giant) hogweed seems the most likely explanation.
It can be pretty nasty. And also once sensitised I think you are always
in for a rough ride with it in future.

No, No, NO!!!

I beg to disagree. I reckon one of hogweed or giant hogweed is about the
most likely at this time of year strimming in rough ground. I did a
quick lookup and it doesn't require any presensitisation the damage is
done by the combination of sunlight and furocoumarins in the sap.

That's all true, but it's NOT particularly likely to be giant hogweed,
or even ordinary hogweed. LOTS of plants will do it to the same
extent, and not everybody reacts to giant hogweed, anyway. Common

Enough people do and badly enough that it is classified as a noxious
weed requiring careful handling.

http://www.dermnetnz.org/dermatitis/plants/hogweed.html

periwinkle and most spurge sap will both do it, for a start.

Most euphorbiaceae will - and some of the succulent ones are
exceptionally nasty and caustic in this respect. A few like E. Virosa
contain sap at such high pressure that if punctured it will jet latex
threads 3-6 feet away from the plant and cause temporary blindness and
intense pain (permanent blindness if you rub your eyes). The sap of
Aeonium Lindleyii is alledgely a partial antidote to it.

Regards,
Martin Brown