Thanks for writing to the forum!
You are either suffering from contact dermatitis or from allergy to some food or sea material. You must get an allergy test done, either a skin test or RAST, to know what you are allergic to.
• Weak acid solutions [lemon juice, vinegar] can be used to counteract the effects of dermatitis contracted by exposure to basic irritants [phenol etc.].
• If blistering develops, cold moist compresses applied for 30 minutes 3 times a day can offer relief.
• Calamine lotion and cool colloidal oatmeal baths may relieve itching.
• Oral antihistamines such as diphenhydramine (Benadryl, Ben-Allergin) can also relieve itching.
• For mild cases that cover a relatively small area, hydrocortisone cream in nonprescription strength may be sufficient.
• Avoid scratching, as this can cause secondary infections.
It is difficult to comment beyond this at this stage, without examining the lip. Do consult a skin specialist. Please let me know if there is any thing else and do keep me posted. Take care!