A swollen lip is usually a sign of allergies, and can emerge two hours after taking a new medication or eating allergen foods like peanuts, seafood, eggs or soy.

Swollen lips may also be a sign of another health condition, like a cold sore, dry or burnt lips, a mucocele or other types of inflammation. You should see a doctor if the swelling persists for over 3 days, however, if you also have difficulty breathing, you should proceed to the emergency room.

Applying ice directly on the lips can help with inflammation and decrease discomfort, however antihistamines may also be useful in some cases. You should follow treatment as prescribed by your doctor.

What causes swollen lips?

The most common causes of swollen lips include:

1. Allergies

A food allergy is the most common reason lips become swollen. It generally occurs about 2 hours after consuming the food allergen. The allergy can also lead to symptoms like coughing, a sensation of a lump in the throat, difficulty breathing and facial redness. Other types of allergies can cause swollen lips, like allergies to make-up medication, dental whitening or plants.

How to treat: Treatment generally involves the use of antihistamines, like cetirizine or loratadine, as prescribed by your doctor. If you have difficulty breathing, you should proceed immediately to the hospital or call an ambulance.

In addition, you are advised to complete allergy testing to investigate what caused the allergy so that you can prevent a reaction in the future. If the allergy was caused by make-up or other cosmetic products, you are advised to avoid use of the product again.

2. Cold sore

A cold sore, caused by a herpes infection, can cause lip swelling, as well as blisters on the lips that feel numb or tingling. Other infections, like thrush, can also cause swollen lips. Lips that are dried or cracked are especially prone to infections, as this can attract microorganisms to the lips and promote growth, leading to further redness, fever and pain.

How to treat: You should see your doctor to evaluate your lips and identify the microorganism causing the infection. Once identified, the doctor can prescribe cold sore medicine in the form of ointments or pills.

Herpes is typically treated with antivirals, like acyclovir, however pain and discomfort can be treated with anti-inflammatories or analgesics, like ibuprofen or acetaminophen.

3. Dry or burned lips

Lips that are burned by the sun, from food, or from acidic foods (like lemons or pineapple) can leading to swelling. This type of swelling can last for a day or two, and is usually accompanied by other symptoms like pain, burning or discoloration. This can also happen with extreme temperature changes in very hot or cold environments.

How to treat: To decrease swelling, apply a moisturizing cream, coconut butter or vaseline directly to areas of dryness or burned skin on the lips.

4. Mucocele

A mucocele is a type of cyst that can lead to a small, swollen lump on the lips. It usually occurs after biting the lips or after a direct blow, and is usually the result of saliva that has accumulated in an inflamed salivary gland. Learn more about the symptoms of a mucocele and how it is treated.

How to treat: Normally, the mucocele disappears on its own within 1 or 2 weeks without any type of treatment. However, if it continues to grow or lasts for longer, you should see a doctor for assessment. The doctor may opt to drain the cyst to accelerate treatment.

5. Tooth abscess

Inflammation in the teeth, from cavities or a tooth abscess, for example, can cause swelling in the gums which can extend to the lips.

In these cases, patients may feel intense pain around the inflamed tooth, which can be accompanied by bleeding, foul breath and even a fever.

How to treat: Tooth inflammation should be assessed by a dentist, who may recommend analgesic medications, antibiotics or, if necessary, a dental procedure. To relieve inflammation on the lips, you can apply a warm compress and take anti-inflammatories, such as ibuprofen.

6. Fall, injury or bruise

A fall or accident can cause an injury to the mouth, which can leave the mouth swollen for a few days until the injured tissues fully heal. The area willy typically be painful to the touch, and the surrounding skin may have purple or reddish marks.

In some cases, the tooth can injure the lip, causing a cut. This is very common in children who are learning to walk or who are running while playing.

How to treat: You can apply cold compresses or chamomile tea bags directly on the lips, two to three times per day to reduce swelling.

7. Impetigo

Impetigo can affect the mouth region, and is often characterized by the presence of small, crusted wounds on the lips or close to the nose. Impetigo is a common childhood infection that is easily transmitted between children. It should be assessed by a pediatrician.

How to treat: You should see a doctor to confirm a diagnosis. Treatment usually involves the use of an antibiotic ointment, although other measures should also be considered, like avoiding picking at the wounds, keeping the area clean, and maintaining adequate overall hygiene.

8. Insect bites

Insect bites on the lips, caused by fleas, ticks or mosquitoes, can cause blisters, inflammation, redness, pain, itching, irritation and even swelling in the affected area.

How to treat: An insect bite is usually a mild reaction that usually resolves on its own within a few days. It is generally recommended to apply a cold compress to the affected area to relieve pain.

However, if the bite is very swollen or very painful, the doctor may prescribe painkillers, a corticosteroid ointment, antihistamines (if the bite triggers other allergy symptoms) and antibiotics (if the bite becomes infected).

9. Mouth ulcers

Mouth ulcers are open wounds or lesions that can appear in any part of the mouth, such as the inside of the cheeks, gums, tongue and lips. They can cause pain and swelling in the affected area.

The causes of mouth ulcers can range from biting the cheek, tongue or lips, burning the mouth with hot food or drinks, wearing braces or chewing tobacco, for example.

How to treat: When treating mouth ulcers, be sure to avoid hot foods or drinks. You can gargling with salt water and eat popsicles to reduce pain..

If the discomfort from the ulcers is very intense, the doctor may recommend analgesics, such as analgesics, while more severe ulcers may require anti-inflammatories or chlorhexidine mouthwash. Learn more about how to treat mouth ulcers quickly.

10. Using braces

The adaptation period after first getting braces can lead to swollen lips.

Other complications that may arise with the placement of braces are difficulty chewing normally due to pain, as well as canker sores or wounds on the lips.

How to treat: To avoid swollen lips from braces, it is important to consult a dentist so that he can recommend the appropriate treatment. This may include the use of dental wax that helps prevent the braces from rubbing against the oral mucosa.

11. Stress

Stress can cause swollen lips due to a combination of physical and psychological factors. As a stress response, the body can trigger the emergence of allergies, dermatitis or angioedema, for example.

Additionally, some people, when stressed, may develop the habit of biting their lips, which can cause irritation and swelling.

How to treat: To combat chronic stress, you are advised to seek psychological support and adopt healthy habits that help reduce symptoms, such as exercising regularly and getting enough sleep.

Other causes

In addition to the above causes, swollen lips can also occur with:

A swollen or infected piercing
Spicy foods
Pre-eclampsia during pregnancy
Canker sores
Keloids
Oral cancer
Cardiac, liver or kidney failure

Given there are so many causes for swollen lips, it is important to seek medical attention, especially if you are unsure why it has occurred.

When to see the doctor

You should especially see a doctor if:

Your lips become swollen very suddenly, and you also notice swelling in the throat and tongue. These can lead to difficulty breathing if left untreated.
If the swelling lasts for over 3 days.
If you notice other symptoms like fever over 38ºC (or 100.4ºF) or have difficulty swallowing
You notice swelling to the entire face or other parts of the body

In these cases, the doctor may need to maintain airway patency to ensure you remain breathing by using medication. However, bloodwork and allergy testing should eventually be ordered to avoid further reactions in the future.