See link and see the bottom of the page for contact dermatitis and photodermatitis effects.

I had photodermatitis problems with parsnips....silly me. I dug up the puny ones never harvested the next spring and ended up with purple burns where the sap from the green leafy portions followed by sun touched my skin - ouch! It seems Spring is the time when the sap runs the most (for parsnips) and the burns are the worst.

I've safely ate parsnips (but that was the root) after that with no ill effects but I cannot say the same would be for you and fennel. Move the plant to where you will have no contact, use gloves, and proceed with a huge helping of caution if you attempt to consume or use fennel in any way. I would suggest avoiding eating or using it altogether, if I was you.

FataMorgana

Here is a link that might be useful: Fennel

From the blisters and the pictures of photodermatitis, that is probably exactly what happened to me. I was out in the sun for a while after transplanting the fennel. Good to know it also can happen with parsnips! I also grow them and usually harvest them all by late winter/early spring. This year, I let some go to seed - I'll be careful around it.

As much as I like eating fennel, I think I may skip it for a while.

Did you keep the blisters out of the sun afterwards? It's been five days, but I'm a little nervous to re-expose them to the sun. Did yours scar at all?

Thanks!
Bellatrix

It took a while to pass and it hurt like the dickens. But no scars. I don't remember if I re-exposed it to sun or not.

FataMorgana