How do i know if i have an allergic reaction or a chemical burn? i used a new face wash and my face is itching, burning and i have small zits showing

Contact dermatitis: This sounds like contact dermatitis. Apply moisturizer daily, also apply 1% hydrocortisone 2-3 times a day until things improve

Can be difficult : Telling the difference between a chemical burn and local allergic reaction can sometimes be tricky, but in general an allergic reaction would rapidly lessen with Benedryl and cool compresses while a burn would be more long lasting and eventually turn into peeling or flaking. Either way, avoiding the wash that caused it would be wise.