hi! thanks for the query..
The swelling of the upper lip
area which has developed so suddenly may be due to the following reasons:
1) Insect Dermtitis : as the name says , you could have developed a contact allergy
to secretions etc of some insect /insect bite.This is a very common cause of a sudden swelling upper lip overnight.
2) Acute allergy: to anything taken orally probably last night or any thing applied last night.
: common after fever etc but can come up without any significant relevant history.
U may definitely apply Mupirocin
on the affected lip area and can do it twice daily for a week .I would also advise you to take an antihistaminic tablet orally ,which would reduce the allergic response
Hope this helps..take care!