What is best to treat allergic reaction lip swelling?

Lip swelling. It is very important to find out what has caused the lip swelling. If it is an allergic reaction, stop taking whatever caused the reaction, and see your physician or an allergy specialist for an evaluation. Do not try and treat this yourself. Also see your dentist to see if there is a dental infection.
Anti-inflammatories. Stop taking whatever caused the reaction. If you have trouble breathing, go to the emergency room. If you don't have trouble breathing, just take some aspiring, Ibuprofen or aleve (naproxen) to reduce swelling.