Hello and thanks for your question. What poison do you have on your eyelids and how did it get there?
Yes, Benadryl can be helpful, but I would recommend using a better OTC antihistamine such as Zyrtec or Allegra or Claritin.
I would also recommend getting some OTC 1% hydrocortisone ointment (not cream) and rubbing that on your eyelids twice daily. In addition, cool compresses over the eyes used liberally can help calm down the inflammation quicker. Usually having poison ivy on the eyelids doesn't cause any permanent eye damage; it's just a pain in the rear for a few days. Does that make sense?
That's all I think you really need to do for right now. Do you have any other questions about this?