[waterbuffalofarmer]

Listen guys you may have heard on the news about hogweed being rampant this year, apparently it is identical to cow parsley and if handled causes third degree burns. Please everyone take care. 

[SallyintNorth]

Read this

It's mainly giant hogweed which is the problem, not the more everyday hogweed.  However, both have sap which can cause burning when on-your-skin-and-exposed-to-sunlight, so keep your arms and legs covered when walking / working where these plants may be, and if you do get into over-close contact with one, wash the skin thoroughly and don't let the sun on that flesh for a few days.

The hogweeds are quite easily distinguished from cow parsley - that link shows you all three.

[lord flynn]

hogweed is not identical to cow parsley -I would hope that anyone with grazing animals (i.e. most on here) would have a clue tbh.

[Bionic]

Thanks for that link Sally. I can now tell the difference and I'm pleased to say we don't have any of the giant type here 

[doganjo]

The leaves show you - "the leaves are very different to hogweed - they are tripinnate (the leaflets are themselves divided and then these divisions are divided again)"

[Fleecewife]

I think most people can tell giant hogweed from any other umbellifer.  The clue is in the name - they are GIANT, taller than men.

[Kimbo]

....yep, its a genuinely GIANT weed and the leaves are pretty hard to mistake too. Don't panic people but be aware of what it looks like X

[Clarebelle]

Please don't dismiss the smaller hogweed which can be just as vicious. My husband was strimming weeds at work the other week, including hogweed (NOT the giant variety) and the next morning his hands and neck were covered in blisters and the skin was red raw. He still has violent purple scars all over his hands two weeks later...

[Fleecewife]

Please don't dismiss the smaller hogweed which can be just as vicious. My husband was strimming weeds at work the other week, including hogweed (NOT the giant variety) and the next morning his hands and neck were covered in blisters and the skin was red raw. He still has violent purple scars all over his hands two weeks later...

Interesting.  I know common hogweed is edible when cooked, but I didn't know the raw sap could still be a bit toxic.  It's the giant stuff though which is aggressively toxic, causing the skin to blister and burn in sunlight.  It's one of those noxious weeds we are supposed to eradicate, but it's all over the place, on roadsides, graveyards, railway embankments and post industrial sites.

[Carse Goodlifers]

...Interesting.  I know common hogweed is edible when cooked, but I didn't know the raw sap could still be a bit toxic.....

I didn't know that you could eat it 
We have quite a bit of it on our access track but I'm slowly dealing with that 
I've never had any reaction to the sap but I think I'll be a bit more careful, especially after reading Clarebelle's post.

[Louise Gaunt]

Normal sized hogweed in Guernsey was notorious for causing skin problems. I had some nasty blisters on my feet when the sap soaked through my trousers when I was strimmimg. I thought I had covered up,properly but wasn't wearing socks in my trainers and got hit with the sap. It was quite painful and I needed to cover he blistered areas for several weeks when out in the sun to avoid photosensitive reaction.

[Hevxxx99]

Normal hogweed is edible (I've eaten it: quite pleasant but not as nice as ground elder) and, as the name suggests, animals love it.  It is high in silicates and is good for hoof formation in horses amongst other things.  Mine love it ad so do the sheep.  I don't have hogs, but I'll bet they do too.

Maybe the small stuff that caused a reaction was juvenile giant hogweed plants.

[SallyintNorth]

Read this

It's mainly giant hogweed which is the problem, not the more everyday hogweed.  However, both have sap which can cause burning when on-your-skin-and-exposed-to-sunlight, so keep your arms and legs covered when walking / working where these plants may be, and if you do get into over-close contact with one, wash the skin thoroughly and don't let the sun on that flesh for a few days.

The hogweeds are quite easily distinguished from cow parsley - that link shows you all three.

I'll quote you some relevant bits from that Woodland Trust page

The sap of giant hogweed contains furocoumarin, which makes skin extremely sensitive to sunlight (phytophotodermatitis). If the sap gets onto your skin, then you are exposed to sun, your skin can blister badly and blistering can reoccur over months and even years.
...
If you do get giant hogweed sap on your skin, be sure to wash the area thoroughly immediately, seek medical advice, and do not expose the area to sunlight for a few days.
...
[Common hogweed] is very similar-looking to giant hogweed but is much smaller. ... This plant only reaches a maximum height of 2 metres (6 ft 7 in) and the symmetrical flower heads only reach 20cm across.

  (Giant hogweed can reach 18 feet.)

It doesn't talk about the furocoumarin being in common hogwood, but I agree with others, I've had a reaction to sunlight on skin that has been in contact with it.