What causes a blood blister on the lip?

Injury to the lip generally causes blood blisters on the lip, states Lip Source. An injury may include pinched or bitten skin. Blood pools under the injured skin causing the blood blister.

A blood blister on the lip does not require medical attention and usually disappears on its own within a week or so, shares Lip Source. Placing ice on the affected area can reduce swelling or pain associated with the injury. If the area becomes infected, a person should see a doctor.

Other types of blisters on the lips include water blisters, lip cancer, sun blisters, fever blisters and cold sores, adds Lip Source. If unclear as to what type of blister is present, an individual should seek medical attention.