Thanks for writing your query.
After reading your post, it seems that cause of your husband's lips swelling can be due to some insect bite or due to some repeated injury
from a sharp tooth.
You should get him examined in a dental clinic.
He can be given an antihistamine like cetrizine
10 mg along with an anti inflammatory like Ibuprofen
I would advise you that get him clinically examined and investigated.
I hope this is helpful to you.