Keep the cortisone creme handy and apply it next time before you work with that rubber. It is probably made with latex and you are allergic to it. When I work in the garden around tomatoes I get the same thing.
I feel your pain! I had a reaction to a new bra! You can imagine where all I broke out! Had to have steroid meds & itch pills for weeks! But I must say it got very bad before I finally went to a derma. to have it checked! Get that cortizone cream on it quickly!
Yikes, this looks like the stuff I used to get when I handled fiberglass. Cortizone for sure, also wear that long sleeve shirt when handling that stuff and remember when you wash clothes to wash those that have come in contact with the rubber separately.This will keep the rubber dust from getting into your other clothing.
What you have is called "Contact Dermatitis" and the cortizone cream and sometimes an allergy pill (OTC) can help. You already knew the rubber caused it so you might want to keep a light weight long sleeve shirt with you on the days you work with that stuff and use cool water on your arms as soon as possible when you are finished. Remember you can still get the rash from your arm just rubbing against your cloths.
Best thing to use is Cortizone Cream to stop the allergic reaction you are having. Get the 2% if available. Be sure to get the cream and not ointment because the cream is quickly absorbed into the skin. Not messy at all. It really helps very quickly.
Marcelle
What about tea applied to the skin? It works for sunburn. I hope it goes away soon. It looks painful.