Waking up with a swollen lip can be an alarming discovery, especially if there wasn’t an obvious mouth injury the day before. In addition to sudden trauma to the mouth, there are several common conditions that can cause swollen lips to appear in the morning. These include a variety of allergic reactions, as well as medical conditions affecting the skin, nerves, or face muscles. Dental work can also trigger inflammation that causes your lips to swell.

Depending on the cause, a swollen lip can develop over several hours. This means you can go to bed with no signs of trouble and wake up looking and feeling much different. And if the cause isn’t obvious, you may need to look for other symptoms or think back to what you were exposed to that might provide an explanation.

A swollen lip is the result of either inflammation or fluid build-up in the tissue of the lip. Discovering the cause of your swollen lip may take some detective work. In most cases, however, a likely cause can be determined pretty easily.

Allergic reactions

Allergies to certain foods, medications, or the bite or sting of an insect are fairly common triggers for swollen lips and other symptoms. Foods often associated with allergies include:

You may also be allergic, or have an extreme sensitivity, to certain spices. Hot peppers may trigger a burning sensation in the mouth and swollen lips, but even milder spices are associated with allergic reactions. Among them are:

  • anise
  • celery
  • coriander
  • fennel
  • parsley

Allergies to certain medications also may cause your lips to swell overnight. Penicillin and other types of antibiotics are among the more common drugs to cause allergic reactions.

Mild reactions can include rashes or itching. More significant reactions include hives, coughing, wheezing, and angioedema. Angioedema is severe swelling of the deeper tissues of the skin, especially in the face and lips.

One of the most dangerous allergic reactions is anaphylaxis. Its symptoms include chest tightness and swelling of the tongue, lips, and airways. This can make breathing difficult.

Generally, anaphylaxis develops quickly in people with highly sensitive allergies, so it may occur soon after eating something or taking a drug to which you are extremely allergic.

Skin conditions and infections

Pimples on or near the lips may cause some temporary lip swelling. Severe swelling can occur if you have cystic acne. This serious type of acne can cause large boil-like lesions anywhere on the body.

Cold sores, herpes infections, and coxsackievirus blisters around the mouth can also cause lips to swell. These changes are symptoms of a virus and may appear overnight, even though the virus has been present in your body for a much longer time.

If you spent the day in the sun without proper protection, you may awaken with serious sunburn. Your lips can swell and crack if they are sunburned. Fortunately, the effects of sunburn on the lips and elsewhere usually subside within a few days.

A common bacterial skin infection known as cellulitis can cause swelling of the lips or any part of the body that’s infected.

Muscle and neurological conditions

A variety of conditions affecting the nerves and muscles of your face can cause you to wake up with swollen lips or similar symptoms.

Embouchure collapse (or embouchure dystonia) can affect trumpet players and other musicians who spend hours with their lips pursed while playing their instruments.

The embouchure is the position of the mouth when using the mouthpiece of a brass or wind instrument. The strain on the mouth muscles can leave the lips swollen and numb.

Melkersson-Rosenthal syndrome is a rare neurological condition that causes swelling in the lips and face, as well as some muscle paralysis. Flare-ups of the disease can happen days or years apart. These flare-ups usually start in childhood or teen years.

The cause of Melkersson-Rosenthal syndrome isn’t well understood, but it’s believed to be genetic in nature.

Dental issues

Dental work, such as braces and other treatments, can result in swollen lips the day after the work is done. An infection of the mouth or gums may also lead to swollen lips and inflammation inside the mouth.

Lip cancer, though not common, can also cause swelling. However, lip cancer usually presents first as a sore on the outside or inside of the lip.

Injury

A direct injury to the lip may cause swelling that can form slowly overnight. Injuries include cuts, scrapes, and bruises.

You may unintentionally injure your lips if you bite or chew on them without realizing it. Also, sleeping in awkward positions or against hard surfaces can put pressure on your lips, causing a temporary swelling while you sleep.

If the cause of your swollen lip is an injury, such as a blow to the mouth or a bad cut, the lip that absorbed most of the trauma will be the most swollen.

If you received numbing shots in your lower lip before dental work, then your lower lip would be the one that’s swollen the next morning.

One condition that tends to develop only in the lower lip is cheilitis glandularis. This is a rare inflammatory condition that tends to affect adult men more than any other group. It’s also associated with lip cancer.

A similar condition called granulomatous cheilitis is another rare inflammatory condition that affects the upper lip, causing swollen bumps.

Melkersson-Rosenthal syndrome also tends to cause swelling of the upper lip, rather than the lower lip.

If your lip swelling is confined to one side of a lip, it’s likely due to an injury to that part of your mouth, or to the presence of a cyst or other growth in that location. If you wake up and notice this, carefully examine your mouth and look or feel for what may be causing one side to be swollen.

You should also be aware that other conditions can cause one side of your mouth to look different than the other. If you wake up and one side of your mouth is drooping, you have excessive drooling, or you’re having trouble with speech, it could be a symptom of a stroke or Bell’s palsy.

Call 911 immediately if you believe you may have had a stroke. Bell’s palsy is a temporary condition that results from injury or inflammation of the facial nerves. It can also paralyze facial muscles. Any paralysis is an emergency and should be evaluated by a doctor. However, Bell’s palsy is not a life-threatening condition.

At-home treatments

Applying an ice pack wrapped in a towel to swollen lips can often reduce the inflammation. Never apply ice directly to skin, as this can cause further damage.

You may find some relief from swollen lips caused by sunburn by using aloe lotion. Severe dryness or cracking may improve with a gentle moisturizing lip balm.

Medical treatments

For swollen lips caused by inflammatory conditions, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil) or corticosteroids may help reduce the swelling.

NSAIDs may also be helpful in the event of a bruise or other injury that’s causing your lips to swell.

Other neurological conditions, such as focal dystonia, may require more invasive treatments. For embouchure dystonia, muscle relaxers such as baclofen (Gablofen) may be useful. Injections of botulinum toxin (Botox) may help, but must be administered with care by a doctor.

A serious food allergy can cause more than a swollen lip. If there are signs of a severe allergic reaction such as wheezing, shortness of breath, or swelling of the mouth or tongue, call 911 or your local emergency number.

A dermatologist should evaluate cystic acne or the presence of cysts or suspicious growths on or beneath the surface of your lip. You may be referred to a different specialist if another condition is suspected.

If you wake up with mildly swollen lips and no other symptoms, pay attention to whether the swelling goes away or continues. If the swelling persists beyond 24 hours, see a doctor. If there are signs of a severe allergic reaction, get emergency medical care.

If you wake up swollen lips with no obvious cause, consider the foods you ate and any medications you took. Also check for injuries, infection, and any possible exposure to allergens in your environment.

Seek emergency medical attention if you experience a serious allergic reaction, a stroke, swelling of the face or eyes, or an infections of the face.