Cracks in the corners of your mouth are almost always a condition called angular cheilitis, an inflammation where the upper and lower lips meet. The root cause is usually moisture buildup in the skin folds at the corners of your mouth, which breaks down the protective outer layer of skin and lets naturally occurring yeast or bacteria move in and cause infection. Sometimes the trigger is obvious, like constant lip-licking in dry weather. Other times, it points to a nutritional deficiency or an underlying health condition worth investigating.
How Moisture Breaks Down the Skin
The corners of your mouth are uniquely vulnerable. Saliva collects there naturally, and every time you eat, talk, or yawn, the skin folds and stretches. When saliva sits on the skin repeatedly, it strips away the outermost protective layer. Once that barrier is compromised, organisms that normally live harmlessly on your skin, particularly a yeast called Candida and the bacterium Staphylococcus aureus, can infect the damaged tissue.
This is why anything that increases moisture at the mouth corners tends to trigger angular cheilitis. Habitual lip-licking is one of the most common culprits. Drooling during sleep, thumb-sucking in children, and even wearing a face mask for long stretches can trap moisture against the skin. Ill-fitting dentures are another major factor, especially in older adults, because they change the way the lips close and create deeper creases where saliva pools.
People with naturally deep folds at the corners of the mouth, sometimes called marionette lines, are more prone for the same reason. Orthodontic braces and other dental appliances can also redirect saliva flow and create the conditions for cracking.
Vitamin and Mineral Deficiencies
If your cracked corners keep coming back or don’t respond to simple moisturizing, a nutritional deficiency may be the underlying cause. Several B vitamins and minerals play direct roles in keeping the skin and mucous membranes healthy, and running low on any of them can show up as angular cheilitis.
The most commonly linked deficiencies include:
- Vitamin B2 (riboflavin): A deficiency causes lip inflammation, light sensitivity, and a swollen tongue alongside cracked mouth corners. It can also impair iron absorption, compounding the problem.
- Vitamin B3 (niacin): Severe deficiency produces skin inflammation, digestive problems, and angular cheilitis.
- Vitamin B6: Low levels are associated with mouth ulcers, a swollen tongue, and cracked corners, along with possible nerve symptoms like tingling.
- Vitamin B12 and folate: Deficiencies in either can cause anemia and mouth inflammation, including angular cheilitis.
- Iron: Iron deficiency is one of the most common nutritional causes worldwide. Along with cracked mouth corners, you might notice fatigue, a sore tongue, brittle nails, or hair thinning.
- Zinc: Low zinc causes skin inflammation, poor wound healing, and angular cheilitis. This is especially common in people with conditions that impair zinc absorption in the gut.
If you’re eating a restricted diet, have heavy menstrual periods, or have a digestive condition that limits nutrient absorption, these deficiencies become more likely. A simple blood test can identify most of them.
Underlying Health Conditions
Angular cheilitis sometimes serves as a visible signal of a deeper health issue. Diabetes is one of the more significant connections: elevated blood sugar impairs immune function and promotes yeast overgrowth, making the mouth corners an easy target for infection. People with poorly controlled diabetes often deal with recurrent episodes.
Inflammatory bowel disease, particularly Crohn’s disease, contributes to angular cheilitis through two pathways. It can cause nutritional deficiencies by impairing the gut’s ability to absorb vitamins and minerals, and it can directly affect wound healing. Conditions that cause chronic dry mouth also raise the risk, because saliva plays a protective role. Adequate saliva levels promote tissue healing and support local immune defense in the mouth. When saliva production drops, as it does with Sjögren’s syndrome, certain medications, or radiation therapy to the head and neck, the mouth corners lose that protection.
Immune suppression from any cause, whether from medications, chemotherapy, or conditions like HIV, increases susceptibility to the yeast and bacterial infections that drive angular cheilitis.
How It Differs From a Cold Sore
Many people mistake angular cheilitis for a cold sore, but they’re different conditions with different causes. Cold sores are caused by the herpes simplex virus and typically start as an itchy or painful area that turns into one or a cluster of small, fluid-filled blisters. They can appear anywhere on or around the lips, and they go through a clear cycle of blistering, weeping, scabbing, and healing.
Angular cheilitis, by contrast, begins as a patch of dry, irritated, or cracked skin specifically at one or both corners of the mouth. It doesn’t form blisters. If untreated, it can progress into swollen, painful sores that may bleed when you open your mouth wide. The location is the biggest clue: if the cracking is confined to the corners where your lips meet, it’s almost certainly angular cheilitis rather than a cold sore.
What Helps It Heal
Treatment depends on what’s causing the problem. Since yeast is the most common infectious agent involved, an over-the-counter antifungal cream applied to the corners of the mouth is often the first step. If bacteria are also involved, which is common, a combined approach targeting both yeast and bacteria works better than treating just one.
Keeping the area dry and protected is equally important. A barrier ointment like petroleum jelly or a zinc oxide cream applied to the corners of the mouth creates a physical shield against saliva. This is especially useful at night, when drooling can keep the area moist for hours. If you wear dentures, having them checked for proper fit can eliminate one of the most persistent triggers.
For cases linked to nutritional deficiencies, the cracks will keep returning until the underlying deficiency is corrected. Supplementing iron, B vitamins, or zinc, depending on what’s low, typically resolves recurrent episodes over a few weeks. When a systemic condition like diabetes or Crohn’s disease is the driving factor, better management of that condition reduces flare-ups.
Why It Keeps Coming Back
Angular cheilitis is notorious for recurring, and this usually means the underlying trigger hasn’t been addressed. If you treat the surface infection but continue licking your lips, wear the same ill-fitting dentures, or remain low in iron, the cracks will return once you stop applying cream. The single most effective prevention strategy is identifying and eliminating the root cause, not just treating the symptom.
For people prone to recurrence, applying a thin layer of petroleum jelly to the mouth corners before bed can reduce overnight moisture damage. Staying on top of nutritional needs, especially iron, zinc, and B vitamins, keeps the skin’s protective barrier intact. And breaking the lip-licking habit, as difficult as that can be, removes one of the most common perpetuating factors.