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Swollen lips are caused by underlying inflammation or a buildup of fluid under the skin of your lips. Many things can trigger swollen lips, from minor skin conditions to severe allergic reactions.

Read on to learn about the possible causes and their additional symptoms and when you should seek emergency treatment.

Anaphylaxis is a severe allergic reaction that can cause swollen lips. Any type of allergy can cause anaphylaxis, and it can happen within minutes or more than half an hour after encountering an allergen. It’s sometimes called anaphylactic shock because it causes your immune system to flood your body with chemicals that can make you go into shock.

Other symptoms of anaphylaxis include:

Anaphylaxis requires immediate treatment with an injection of epinephrine (EpiPen). If you know you have allergies, talk to your healthcare provider about getting a prescription for a portable epinephrine injection that you can carry with you. Make sure your close friends, coworkers, and family members know how to recognize the signs of anaphylaxis and use epinephrine.

Most of the other causes of swollen lips don’t need emergency treatment, but you should still follow up with your healthcare provider to make sure there’s nothing else going on.

Allergies are your body’s reaction to certain substances. When you encounter something you’re allergic to, your body produces a chemical called histamine. The release of histamine can lead to classic allergy symptoms, such as sneezing, itchy skin, and inflammation. This inflammation may cause swollen lips. There are several types of allergies, and all of them can cause your lips to swell.

Environmental allergies

You may have an allergic reaction to substances in the environment. These are often unavoidable and include pollen, mold spores, dust, and pet dander.

Other symptoms of environmental allergies include:

  • swelling in other parts of the body
  • wheezing
  • hives
  • eczema
  • sneezing
  • nasal congestion

An allergist can help treat environmental allergies. They’ll perform skin or blood tests to determine what you’re allergic to. Based on the results, they may recommend an over-the-counter or prescription antihistamine. If your allergies are severe, you may need allergy shots.

Food allergies

Food allergies are a common cause of swollen lips. According to the American College of Allergy, Asthma, and Immunology (ACAAI), about 4 percent of adults and up to 6 percent of children have food allergies. The swelling usually starts as soon as you eat something you’re allergic to. Many foods can trigger allergies, especially eggs, nuts, dairy and shellfish.

Food allergies can also cause:

  • facial swelling
  • tongue swelling
  • dizziness
  • trouble swallowing
  • nausea
  • stomach pain
  • coughing
  • wheezing

The only way to treat food allergies is to avoid foods you’re sensitive to. If you experience swollen lips after eating a meal, keep a food diary and note any allergy symptoms you have. This can help you narrow down what’s causing your allergies.

Other allergies

Insect bites or stings may also cause swollen lips. If you’re allergic to bees, for example, you might have swelling throughout your body after being stung. A quick-acting allergy medication, such as diphenhydramine (Benadryl), can help reduce swelling and itching after an insect bite or sting.

Drug allergies can also cause swollen lips. One of the most common causes of drug allergies, according to the ACAAI, is penicillin. About 10 percent of people are allergic to this common antibiotic. Other possible causes of drug allergies include other types of antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), and anticonvulsants. Some people undergoing cancer treatments also find they’re allergic to chemotherapy drugs.

Other symptoms of drug allergies include:

  • skin rash
  • hives
  • wheezing
  • general swelling
  • vomiting
  • dizziness

Like food allergies, the best way to treat allergic reactions to medications is to avoid them.

Shop OTC antihistamines for mild allergic reactions.

Angioedema is a short-term condition that causes swelling deep under your skin. It can be caused by allergies, nonallergic drug reactions, or hereditary conditions. The swelling can affect any part of your body, but it’s most common in your lips or eyes.

Other symptoms of angioedema include:

  • itching
  • pain
  • hives

Angioedema symptoms usually last for 24 to 48 hours. It’s treated with antihistamines, corticosteroids, or epinephrine injections. Your doctor can help you determine the right medication based on the cause and severity of your angioedema. Antihistamines tend to work well for allergy-related angioedema. Nonallergic and hereditary angioedema usually respond well to corticosteroids.

Injuries to the face, especially around your mouth or jaw, can cause swollen lips.

Causes of facial injuries include:

Depending on the type of injury, you may also have bruising, scrapes, and bleeding.

Treating injury-related swollen lips depends on the cause. For mild injuries, applying an ice pack can help with pain. You can also apply heat to reduce swelling. If you have a deep cut or can’t stop the bleeding, seek treatment at an emergency department or urgent care clinic right away. Also, keep an eye out for signs of infection, such as swelling, heat, redness, or tenderness. Tell your healthcare provider if you notice any of these symptoms.

Cheilitis glandularis is an inflammatory condition that only affects the lips. According to the Genetic and Rare Diseases Information Center, it’s most common in men. Doctors aren’t sure what causes it, but it seems to be associated with UV exposure, lip injuries, and smoking.

Other lip symptoms include:

  • tender lips
  • pin-sized holes that excrete saliva
  • uneven lip surface

Cheilitis glandularis often doesn’t need treatment. However, it does make you more prone to bacterial infections. These usually need to be treated with antibiotics or corticosteroids.

Melkersson-Rosenthal syndrome (MRS) is an inflammatory neurological condition that affects the face. The main symptom of MRS is swollen lips. In some cases, it can also cause a fissured tongue or facial paralysis. Most people only experience one or two of these symptoms at a time.

MRS is rare and likely genetic. It’s commonly treated with corticosteroids and NSAIDs to help reduce swelling.

Cheilitis granulomatous, sometimes called Miescher cheilitis, is another possible cause of swollen lips. It’s a rare inflammatory condition that causes lumpy swelling in your lips. Doctors often refer to it as a subtype of MRS.

Like MRS, cheilitis granulomatous is usually treated with corticosteroids and NSAIDs, which can help reduce swelling.

Several things can cause your lips to swell, from common allergies to rare genetic conditions. Work with your healthcare provider to figure out the underlying cause so you can treat it or avoid it in the future. In the meantime, taking over-the-counter NSAIDs, such as ibuprofen (Advil), may help reduce swelling.