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Full lips might be popular among Hollywood stars, but for the rest of us, swollen lips may be a sign of a problem. Lips usually swell due to trauma or allergies, though some swollen lip causes are more serious.

What Happens When Your Lip Swells?

When lips swell, it’s due to the blood vessels that supply them filling with blood. The structure of the lips includes the thin, delicate skin that covers the outside and the muscle that lies underneath, which is filled with blood vessels. The final, inner layer of the lips is called the oral mucosa, and it’s part of the mucous membrane that lines the mouth. When blood rushes to the lips in response to trauma, allergic reaction or infection, the additional blood makes the lips swell.

Swollen Lips and Injuries

Even minor trauma that doesn’t break the skin can cause the lips to swell, like sports injuries. It’s also easy to hurt your lips bumping into things or through other minor accidents. The swelling usually goes down without treatment, but sometimes swelling hides other injuries, like cuts and abrasions that can become infected or make chewing and speaking difficult.

Swollen Lips and Allergic Reactions

Pollen, medications, dyes and certain trigger foods and drinks can cause allergic reactions that include swollen lips. The University of Maryland Medical Center (UMMC) explains that when the body experiences an allergic reaction, it produces histamine. This chemical causes the blood vessels in the lips to swell. Other symptoms of an allergic reaction are red, itchy welts known as hives, a swollen or tight throat, breathing difficulties, muscle pain, fever, and rashes or discoloured patches on the feet, hands or face. If you think you are suffering from a serious allergic reaction, it is best to seek medical attention immediately.

When to See a Doctor for Swollen Lips

Swollen lips can sometimes return to normal without treatment, but if you also experience more serious symptoms, like breathing difficulties or heavy bleeding, get immediate medical attention. Other reasons to see a doctor include if the swelling continues for longer than a few days or if it’s accompanied by pain or fever, which may mean your lips are infected. Also, see a doctor if the swelling has no clear cause or if it comes and goes for no apparent reason.

Swollen lips are usually more inconvenient than serious, but if you have other, more severe symptoms, see a doctor right away. An allergic reaction can turn life-threatening quickly, and serious swelling can also be a sign of another harmful medical condition. In most cases though, icing an injury and keeping the area clean may heal your lips in no time.