Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern.
As per your complain the most common cause of sudden occurrence of a bump over lip can be due to some bug bite or
allergic reaction to any food or atmospheric allergen..
Another cause can be Viral infection caused by herpes virus 1 causing
cold sore which is also recurring as well as appears as
fluid filled blisters.
The exact cause can be confirmed by consulting a
Dermatologist when there is eruption and getting proper evaluation and investigation done,
If there is allergic reaction he/she can advise you to take anti-allergic medication like Cetrizine or
fexofenadine [allegra] for relief.
If there is pain you can also take anti-inflammatory painkiller like Ibuprofen.
Do cold compresses..
For viral infection anti-viral medication like Acyclovir oral and topical can be advised..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.