Answer:
You will know when your lip piercing is infected when your lip is totally swollen and you cannot tolerate the pain. When you touch it, it is extremely painful that you can no longer eat properly. When you see yellowish fluid coming out when you kinda push and put pressure on it, that's is one definite sign, it is infected. Fever will occur in some cases. You should clean it more frequently to avoid infection. =) Hope this will help you.