Hi..
Welcome to HEALTHCARE MAGIC..
As per your complain a sudden swelling of the lip can be an Allergic
Angioedema that can be caused due to any insect or
bug bite or
allergic reaction to any food or medicine..
You should consult his treating physician and get evaluated and as the allergic reaction i treated with anti-allergics but anti-allergics can increase the risk of epileptic attack so it can be given to him only after advise from his physician, although newer anti allergics like
loratidine or fexoenadine has lesser side effects..
But the best way will be consulting his treating physician as he knows him complete medical background and will advise accordingly..
As of now you can do
cold compresses over the lip for relief from swelling..
If there is pain a numbing gel can be applied.
Avoid biting or pressing the lip.
Drink plenty of water to lighten the effect of the irritant..
Hope this information helps..
Thanks and regards..
Dr.Honey Nandwani Arora.