Why Are the Corners of My Mouth Cracked?
The honest verdict
This is usually not an allergy
Cracked corners of the mouth — medically known as angular cheilitis — is rarely caused by an allergy. The most common trigger is a moist environment from drool or lip-licking, which allows yeast (Candida) or bacteria to overgrow. Other frequent causes include dry or cold weather, vitamin B or iron deficiency, and poorly fitting dentures. Allergic reactions to lip balms, toothpaste, or makeup can cause cracking, but they are less common and usually accompanied by itching, redness, or swelling of the lips themselves.
This is a general research summary, not a diagnosis. It can't tell you what's causing your symptom — a clinician can.
Check this first
When cracked corners of the mouth is an emergency
Most of the time this can be handled calmly. But a few signs mean you shouldn't wait. Match what you're seeing to the right level of care below.
If any emergency sign below is present, call 911 or go to the ER now.
- Emergency
Cracking with swelling of the lips, face, or tongue, or trouble breathing — call 911; this can be anaphylaxis (rare, but possible with a severe allergic reaction).
Call 911 or go to the ER now
- Urgent
Cracked corners with spreading redness, warmth, swelling, or red streaking — go to urgent care or ER (possible cellulitis, a spreading skin infection).
Get seen today — urgent care or same-day visit
- Urgent
Cracking accompanied by fever, pus, or severe pain — seek medical evaluation (possible deep infection requiring antibiotics).
Get seen today — urgent care or same-day visit
- See a doctor
Cracking that does not improve with home care (moisturizing, antifungal cream) after 2 weeks — see a clinician to rule out infection, deficiency, or other causes.
Book a routine visit with a clinician
- See a doctor
Recurrent or persistent cracking with symptoms of nutritional deficiency (fatigue, pale skin, sore tongue, or unusual cravings) — see a clinician for blood tests.
Book a routine visit with a clinician
When in doubt, err toward getting seen. These tiers are a general guide, not a substitute for a clinician's judgment about your specific situation.
Key facts
Angular cheilitis affects about 0.7-3.8% of the general population, but rates are higher in older adults, especially those with dentures.
Candida albicans is the most common cause of angular cheilitis, found in up to 80% of cases.
Vitamin B2 (riboflavin) deficiency is a known cause of angular cheilitis, along with other oral symptoms like a sore tongue and cracked lips.
National Institutes of Health (NIH) — Office of Dietary Supplements
What's causing it
The same symptom can come from very different places. Here are the usual suspects for The corners of the mouth (oral commissures) — the skin folds where the upper and lower lips meet, tagged by mechanism and how common each one is — so you can see where an allergy actually fits.
Moisture and irritation (drool or lip-licking)
Frequent licking of the lips or drooling during sleep keeps the corners of the mouth moist, breaking down the skin barrier. This creates a warm, damp fold where yeast (Candida) or bacteria can thrive, leading to cracking, redness, and soreness.
Yeast infection (Candida) or bacterial infection
Angular cheilitis is often caused by an overgrowth of Candida albicans (the same fungus that causes oral thrush) or bacteria like Staphylococcus aureus. It appears as red, cracked, sometimes crusted lesions at the corners of the mouth and may be accompanied by a white coating on the tongue.
Dry or cold weather
Wind, cold air, and low humidity can dry out the lips and the skin at the corners of the mouth, leading to chapping and cracking. This is often seasonal and improves with moisturizing lip balms and protection from the elements.
Nutritional deficiency (vitamin B or iron)
Low levels of riboflavin (vitamin B2), vitamin B12, or iron can make the skin at the corners of the mouth more prone to cracking. This is more common in people with restrictive diets, malabsorption conditions, or certain chronic illnesses.
Ill-fitting dentures or orthodontic appliances
Dentures that do not fit properly can change the bite and create a fold at the corners of the mouth where saliva accumulates. This persistent moisture can lead to angular cheilitis, especially in older adults.
Allergic reaction (contact dermatitis)
An allergic reaction to ingredients in lip balms, lipsticks, toothpaste (e.g., flavorings, preservatives, or metals), or even nickel in dental braces can cause redness, itching, and cracking at the corners of the mouth. This is less common than irritant or infectious causes and typically involves other symptoms like swelling or a rash on the lips.
Is this an allergy? Usually, no
It's a common assumption, so it's worth being clear about — and pointing you toward what's more likely going on.
Cracked corners of the mouth is usually not an allergy. The most common cause is angular cheilitis — a condition driven by moisture, yeast, or bacteria, not an immune reaction. Allergic contact dermatitis from lip balms, toothpaste, or makeup is a possible but less common cause, and it typically involves itching, redness, or swelling of the lips themselves. If you suspect an allergy, switching to fragrance-free, hypoallergenic products can help identify the trigger. A true allergic reaction that causes swelling of the lips or throat with trouble breathing is a medical emergency.
Because an allergy is unlikely to be the driver, the most useful next step is a clinician who can look at the actual cause — not an allergy test.
Relief you can try at home
If your symptom is mild and you have no red-flag signs, these gentle steps often help. They soothe — they don't replace figuring out the cause.
- 1
Keep the area clean and dry
Gently wash the corners of your mouth with warm water and pat dry after eating, drinking, or brushing your teeth. Avoid licking your lips, as saliva can worsen the irritation.
- 2
Apply a barrier ointment
Use a petrolatum-based lip balm (like Vaseline or Aquaphor) or zinc oxide ointment to protect the skin from moisture and promote healing. Apply several times a day, especially before bed.
- 3
Try an over-the-counter antifungal cream
If the cracking appears red and moist (suggesting a yeast infection), an OTC antifungal cream containing clotrimazole or miconazole can be applied to the corners of the mouth twice daily for 7-14 days. Use a clean fingertip or cotton swab.
- 4
Address nutritional gaps
If you suspect a deficiency, consider a B-complex vitamin or iron supplement after consulting a clinician. Eating foods rich in B vitamins (eggs, dairy, leafy greens, whole grains) and iron (red meat, beans, spinach) may also help.
- 5
Switch to fragrance-free, hypoallergenic products
If an allergic reaction is suspected, stop using lip balms, lipsticks, or toothpaste with fragrances, flavors, or preservatives. Choose products labeled 'hypoallergenic' or 'for sensitive skin' and see if the cracking improves.
Stop any step that makes things worse. If the symptom isn't easing within a few days, check in with a clinician.
When to see a doctor
See a clinician if cracked corners of the mouth do not improve after 2 weeks of home care, or if they are accompanied by spreading redness, warmth, swelling, pus, fever, or severe pain — these can signal a spreading infection (cellulitis). Also see a doctor if you have symptoms of nutritional deficiency (fatigue, pale skin, sore tongue) or if the cracking keeps coming back. Sudden swelling of the lips, face, or tongue with trouble breathing is a medical emergency — call 911.
❓Frequently Asked Questions
Angular cheilitis itself is not contagious, but the yeast (Candida) or bacteria (Staphylococcus) that cause it can be spread through direct contact, such as kissing or sharing utensils. If you have an active infection, avoid close contact with others until it heals, and do not share lip balms, towels, or drinking glasses.
Yes — deficiencies in riboflavin (vitamin B2), vitamin B12, or iron can make the skin at the corners of the mouth more prone to cracking. This is more common in people with restrictive diets, malabsorption conditions (like celiac disease), or chronic illnesses. A blood test can confirm a deficiency, and supplementation often resolves the cracking.
Angular cheilitis causes cracking, redness, and sometimes crusting at the corners of the mouth, usually on both sides. Cold sores (herpes simplex) typically appear as small, fluid-filled blisters on or around the lips, often on one side, and may tingle or burn before they appear. Cold sores are contagious and caused by a virus; angular cheilitis is usually caused by yeast or bacteria.
Yes — some people are allergic or sensitive to ingredients in toothpaste, such as sodium lauryl sulfate (a foaming agent), flavorings (cinnamon, mint), or preservatives. This can cause a contact dermatitis that leads to redness, itching, and cracking at the corners of the mouth. Switching to a toothpaste without sodium lauryl sulfate or artificial flavors may help.
With proper treatment — keeping the area dry, using a barrier ointment, and applying an antifungal cream if needed — angular cheilitis often improves within a few days and heals completely in 1-2 weeks. If it persists longer, or if it keeps coming back, see a clinician to check for underlying causes like nutritional deficiency or ill-fitting dentures.
Medically reviewed by
Dr. Chet TharpeMD
Last reviewed July 2026
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Read moreThe best next step is a real clinician
This symptom is usually not driven by an allergy, so an allergy test won't give you the answer. A primary care doctor or the right specialist can examine what's actually going on and guide you from there.
Curex focuses on at-home allergy testing and immunotherapy, which isn't the right fit for this symptom — and never a substitute for medical care.
- 1DermNet — Angular Cheilitis
- 2American Academy of Dermatology (AAD) — Angular Cheilitis: Causes and Treatment
- 3Mayo Clinic — Angular Cheilitis: Symptoms and Causes
- 4Cleveland Clinic — Angular Cheilitis: Causes, Symptoms & Treatment
- 5National Institutes of Health (NIH) — Riboflavin Fact Sheet for Health Professionals
This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. It cannot tell you what is causing your cracked corners of the mouth or whether it is an allergy. If you have any emergency sign — trouble breathing, fast-spreading swelling, sudden weakness or confusion, or severe pain — call 911 or go to the nearest emergency room. For anything that is new, worsening, or persistent, see a licensed healthcare provider. Curex focuses on at-home allergy testing and immunotherapy, which is not the appropriate care for this symptom and never a substitute for a clinician.