4 year old had hives. gave benadryl (diphenhydramine) at 6 pm. woke up at 12 with much worse hives whole body. 2nd dose of benadryl (diphenhydramine). 1:30 vomit. no fever. ?

Infection or meds: Hives this bad are usually due to recent/ ongoing infection or medication. Til you sort that out try zyrtec (cetirizine) ( otc) which is longer acting. If the vomiting cont, be sure to push gatorade etc to keep salt balance etc. Hope this helps.

Allergic to: Something. You may want to have her checked out . In the meantime , continue with your Benadryl (diphenhydramine) every 6 hours till seen by pediatrician. Also take pictures, cus it always never fails, the hives will be gone by the time you see your doctor.