What causes a blister on your lip?

There are several potential causes for blisters on the lip, including:

1. Infection: Viral infections such as herpes simplex virus (HSV-1) and canker sores can cause blisters on the lip. HSV-1 is the most common cause of lip blisters and can cause recurrent outbreaks.

2. Sunburn: Excessive exposure to ultraviolet (UV) radiation from the sun can cause sunburn, which can lead to blisters on the lips.

3. Allergic reactions: Allergies to certain foods, medications, or other substances can cause blisters on the lips. Common allergens include nuts, shellfish, dairy products, and certain medications such as penicillin.

4. Trauma: Physical injury to the lip, such as a bite, cut, or burn, can cause blisters to develop.

5. Vitamin deficiency: A deficiency of certain vitamins, such as vitamin B12, can lead to blisters on the lips.

6. Autoimmune diseases: Some autoimmune diseases, such as lupus, can cause blisters on the lips.

7. Medications: Certain medications, such as chemotherapy drugs, can cause blisters as a side effect.

It's important to accurately diagnose the cause of a lip blister to receive the appropriate treatment. If the blister is severe or does not resolve within a few days, it's advisable to consult a healthcare professional for proper diagnosis and management.