Dyed hair on monday and it is wednesday now forehead and sides are swollen, taking benadryl (diphenhydramine) and cold compress, how long until swelling goes down?

Dye sensitivity: Likely allergic to hair dye (usually the phenylenediamine component). This is a ''delayed hypersensitivity" unlikely to respond to benadryl (diphenhydramine) and unlikely to improve if exposure continues (wash out thoroughly). A physician would need to confirm by examination and patch testing to confirm. Treatment depends on severity. High potency topical steroid vs other topical immune suppressant vs other.