Lip Sore: Types, Causes and Treatment

Types of lip sore

The quickest way to identify a lip sore is where it sits and what it looks like.

Cold sores

Cold sores are caused by herpes simplex virus type 1. After the first infection, usually in childhood, the virus stays dormant in a nerve and can reactivate. Triggers include colds and fever (hence "fever blister"), sunlight, stress, tiredness, menstrual periods and lip injury.

A typical cold sore:

1. Tingling or burning at one spot on the lip border for a few hours to a day.
2. Small blisters appear in a cluster.
3. Weeping and bursting after 1 to 2 days, leaving a shallow, painful sore.
4. Crusting over the next few days.
5. Healing without a scar, usually within 7 to 10 days.

They are contagious from the first tingle until fully healed. Avoid kissing, sharing cups or lip balm, and oral sex during an outbreak. Never kiss a newborn baby when you have a cold sore. See also oral herpes.

Sores inside the lip

Canker sores (aphthous ulcers)

Aphthous ulcers are shallow, painful, round ulcers with a white or yellow base and a red halo. They form on the soft lining inside the lips and cheeks, never on the outer lip border. They are not caused by a virus and are not contagious. Triggers include minor injury, stress, acidic or spicy foods, sodium lauryl sulfate in toothpaste, and deficiencies of iron, vitamin B12 or folate. Frequent ulcers can be linked to celiac disease, Crohn's disease or Behçet disease.

Lip bite sores: the medical term

The medical term for a sore from biting your lip is a traumatic ulcer. Accidentally biting the lip, a sharp tooth edge, braces, a hot drink or hard brushing can cause one. It looks like an irregular ulcer at the spot of the injury and heals within 1 to 2 weeks once the cause is removed.

A bite can also damage a tiny salivary gland in the lip. Saliva leaks into the tissue and forms a mucocele: a painless, soft, bluish or clear bubble, usually on the inner lower lip. Mucoceles may burst and refill. Those that persist can be removed by a dentist or oral surgeon.

Sores at the corners of the mouth

Angular cheilitis causes red, cracked, sore splits at one or both corners of the mouth. Saliva pools in the folds, which leads to irritation and infection with yeast (Candida) or bacteria. It is more common in people who lick their lips, wear dentures, have deep mouth folds, have diabetes, or are low in iron or B vitamins.

Sore on lower lip: what it can mean

The lower lip gets the most sun and the most bites, so it is the commonest spot for several sores:

• Bite or trauma ulcers and mucoceles inside the lip
• Cold sores on the lip border
• Actinic cheilitis: sun damage that makes the lower lip dry, rough, scaly, pale or blurred at the border. It is precancerous and needs treatment.
• Lip cancer: squamous cell carcinoma of the lip is far more common on the lower lip. It looks like a crusted sore, ulcer or firm lump that does not heal and may bleed. Risk factors are long-term sun exposure, fair skin, tobacco (including pipe smoking and chewing) and a weakened immune system. See oral cancer.

Less common causes of lip sores

• Impetigo: a bacterial skin infection with honey-colored crusts around the mouth, common in children.
• Hand, foot and mouth disease: ulcers in the mouth with spots on the hands and feet, mainly in young children.
• Syphilis: a painless, firm ulcer (chancre) can form on the lip 2 to 12 weeks after oral sex.
• Allergic or irritant reactions: to toothpaste, lipstick, lip balm ingredients or foods.
• Medicines: some chemotherapy and other drugs cause mouth ulcers.
• Skin and autoimmune diseases: lupus, lichen planus, pemphigus.

How lip sores are diagnosed

Most lip sores are diagnosed by appearance and history. Your doctor or dentist will ask how the sore started (tingling, injury, sunburn), how long it has been there, whether you get them often, and about other symptoms. Tests are used when the picture is unclear:

• a swab of a blister for herpes virus testing
• blood tests for iron, B12, folate and celiac disease if ulcers keep returning
• a swab for yeast or bacteria in angular cheilitis
• a biopsy for any sore that has not healed after 3 weeks or looks suspicious

Lip sore treatment

Cold sores

• Start early: antiviral cream such as docosanol or acyclovir works best at the first tingle. Follow the label.
• Prescription antiviral tablets can shorten an outbreak, and are used for frequent or severe outbreaks.
• Pain relief: acetaminophen (paracetamol) or ibuprofen, following the label dose.
• Keep it clean: do not pick crusts, and wash your hands after touching the sore.
• Prevent recurrences: use lip balm with SPF 30 or higher, since sunlight is a common trigger.

Canker sores and bite ulcers

• Rinse with warm salt water several times a day.
• Use an over-the-counter protective gel or a numbing gel containing benzocaine. Do not use benzocaine in children under 2.
• Avoid acidic, salty, spicy and crunchy foods until healed.
• Use a soft toothbrush and a toothpaste without sodium lauryl sulfate.
• See a dentist about sharp teeth, broken fillings or rubbing braces.

Cracked corners

• Apply a barrier ointment such as petroleum jelly.
• Use an antifungal cream if yeast is likely. A pharmacist can advise.
• Treat the cause: refit dentures, correct iron or vitamin deficiencies, control diabetes.

Sun-damaged lips

Actinic cheilitis is treated with prescription creams, freezing, laser or surgery. Lip cancer is treated with surgery, sometimes with radiotherapy.

Frequently asked questions

What does a sore on the lower lip mean?

Most often it is a bite ulcer, a mucocele from a damaged salivary gland, or a cold sore. Persistent dryness, scaling or a sore that does not heal on the lower lip can be sun damage (actinic cheilitis) or, less often, lip cancer. Any lip sore lasting over 3 weeks needs checking.

What is the medical term for a lip bite sore?

A sore caused by biting the lip is called a traumatic ulcer. If the bite damages a minor salivary gland, a fluid-filled bubble called a mucocele can form, usually on the inside of the lower lip.

How can I tell a cold sore from a canker sore?

Cold sores appear on the outside of the lip, start with tingling and form a cluster of blisters that crust over. They are contagious. Canker sores are single shallow ulcers inside the mouth with a white base and red rim, and they are not contagious.

How long does a lip sore take to heal?

A cold sore usually heals in 7 to 10 days. Canker sores and bite ulcers heal in about 1 to 2 weeks. Cracked corners improve within days of treating the cause. Any sore lasting more than 3 weeks should be seen by a doctor or dentist.

Can stress cause sores on the lips?

Yes. Stress is a well-known trigger for cold sore outbreaks and canker sores. It does not cause a new herpes infection, but it can reactivate the virus already living in your nerves. Stress can also make you more likely to bite or chew your lip.

Should I pop a cold sore blister?

No. Popping or picking a cold sore spreads the virus, can cause a bacterial infection and may lead to scarring. Let it crust and heal on its own, keep it moist with a little petroleum jelly, and wash your hands after touching it.