Common causes of pus in the lips include an infection from a lip piercing, a cold sore infection tied to the type I herpes simplex virus, or a condition called cheilitis that can result from certain vitamin deficiencies. Pus is a sign that the body is actively fighting an infection, which may range from mild to serious. Colors of pus range from white to pale yellow, and it forms as a result of immune cell decay during the body's natural response to harmful bacteria. Blisters containing pus usually indicate an infection that can be spread from one person to the next, so dermatologists often advise sufferers to take careful measures for preventing this problem.
Symptoms of a lip infection often include swelling and pain, and this issue is especially common in lip piercings that have not been kept clean. The lips are particularly sensitive areas of the body for piercing due to their frequent contact with food and other objects. Professional piercers recommend that a new piercing is cleaned carefully with antibacterial liquid soap after every meal and any time after the wearer touches it. Signs of a bacterial invasion at the piercing site include pus, along with redness and discomfort. Minor infections often clear up on their own, although more serious ones may need treatment with antibiotics.
Cold sores are caused by a common herpes virus, and they can cause pus in the lips in some cases. This type of blister normally forms on the upper or lower lip and can be quite uncomfortable. While sufferers can be tempted to pop or lance a cold sore, doing so can easily introduce bacteria into the sore and make the initial problem worse. Pus in an infected sore indicates a more serious bacterial infection that normally takes longer to clear up and can sometimes leave a scar.
Cracks or small blisters at the corners of the mouth are often a sign of cheilitis, a common problem resulting from too little vitamin B12 or iron in the diet. Picking or scratching at these sores can also frequently trigger a bacterial infection that can spread. Just as with a cold sore, medical professionals advise that a cheilitis sore is kept clean and left alone as much as possible to facilitate the healing process.