How to get my lip swelling down after shellfish?

Antihistamine: Usually an antihistamine such as Benadryl (diphenhydramine) will do the trick. You should stay away from all shell fish from now on since subsequent allergic reactions may be more severe.

See an allergy doc: Sounds like you have a shellfish allergy. This is dangerous because you could eventually have a serious anaphylactic reaction which is a serious form of allergy attack. I would avoid shellfish and consult with an allergy doctor. For results right now, dyphenhydramine (aka benadryl) is a very effective allergy medication.