Cracks in the corners of your mouth are almost always a condition called angular cheilitis, an irritation and breakdown of skin right where your upper and lower lips meet. The root cause is surprisingly simple: saliva pooling in the skin folds at the corners of your mouth, where digestive enzymes in the saliva gradually break down the skin. Once that skin is damaged, fungi and bacteria move in and make it worse. Nutritional deficiencies account for about 25% of all cases.
How Saliva Starts the Problem
Saliva contains enzymes designed to start breaking down food. When it sits against the thin skin at the corners of your mouth for extended periods, those same enzymes break down skin cells. This creates raw, irritated patches that crack when you open your mouth to eat or talk. Nearly all cases of angular cheilitis begin with this kind of irritant contact, even before any infection takes hold.
Anything that increases moisture buildup at the mouth corners sets the stage. Lip licking is a common trigger, since it deposits saliva in those creases repeatedly throughout the day. Drooling during sleep, mouth breathing, and wearing face masks for long periods can all trap moisture in the same spots. Ill-fitting dentures are one of the most well-documented risk factors, particularly in older adults, because they change the shape of the mouth and create deeper folds where saliva collects.
Infection Makes It Worse
Once the skin is compromised, microbes thrive in the warm, moist environment. The most common pattern is a mixed infection involving both yeast (typically Candida) and bacteria like Staphylococcus aureus or Streptococcus. This combination is why the cracks often get redder, crustier, and more painful over time rather than healing on their own. The infection creates a cycle: inflammation deepens the skin fold, which traps more moisture, which feeds more microbial growth.
Nutritional Deficiencies Behind the Cracks
About one in four cases of angular cheilitis traces back to a nutritional gap. The specific deficiencies most strongly linked to the condition are iron deficiency and low levels of several B vitamins: riboflavin (B2), niacin (B3), pyridoxine (B6), and B12. Low protein intake is also a contributing factor. These nutrients play key roles in maintaining skin integrity and immune function, so when they’re depleted, the skin at the corners of your mouth becomes more vulnerable to breakdown and slower to repair itself.
If your cracks keep coming back despite treatment, a blood test to check iron and B vitamin levels is a reasonable next step. For deficiency-related cases, dietary changes alone can resolve the problem. Foods rich in iron (red meat, lentils, spinach), B vitamins (eggs, dairy, whole grains), and protein help restore what’s missing.
Who Gets It Most Often
Older adults are the most affected group because aging naturally changes the anatomy around the mouth. Skin loses elasticity, facial volume decreases, and the corners of the mouth develop deeper creases. These structural changes make saliva pooling almost inevitable for some people. This is also why recurrence is so common in older adults: the underlying anatomy doesn’t change, so the conditions that caused the problem persist even after treatment clears it up.
People with diabetes face higher risk because elevated blood sugar promotes yeast overgrowth and slows wound healing. Inflammatory bowel conditions like Crohn’s disease can also increase susceptibility, partly through nutrient malabsorption. Anyone on antibiotics or immunosuppressive medications may develop angular cheilitis because these drugs shift the balance of normal skin microbes, giving yeast room to flourish.
Angular Cheilitis vs. Cold Sores
It’s easy to confuse the two since both appear near the lips, but they’re different conditions with different causes. Cold sores are caused by herpes simplex virus and can appear anywhere on or around the lips. They typically start as a cluster of small fluid-filled blisters that eventually burst and crust over. Angular cheilitis stays strictly in the corners of the mouth, looks more like cracked or split skin (sometimes with redness or crusting), and does not involve blisters. Cold sores also tend to tingle or burn before they appear, while angular cheilitis usually starts as dryness and tightness at the corners before cracking develops.
How It’s Treated
Treatment depends on what’s driving the infection. For yeast-related cases, a topical antifungal cream applied to the corners of the mouth is the standard approach. When bacteria are involved, a topical or oral antibiotic targets that component. Since most infections are mixed, your provider may prescribe both. If the area is significantly inflamed, a mild steroid ointment can reduce swelling and discomfort while the antimicrobial treatments work.
For milder cases, especially those caused primarily by saliva irritation rather than heavy infection, simple measures can be enough. Applying a thick emollient ointment or lip balm frequently creates a physical barrier between the saliva and the skin, giving it a chance to heal. Staying well hydrated also helps, since dehydration can make lips drier and more prone to cracking. Most cases improve within one to three weeks with consistent treatment.
Preventing Recurrence
Angular cheilitis is notorious for coming back, especially if the underlying cause hasn’t been addressed. The most effective long-term strategy is reducing moisture buildup at the corners of your mouth. A barrier ointment like petroleum jelly applied before bed can protect the skin overnight, when drooling or mouth breathing is hardest to control. If you wear dentures, having them refitted so they support the natural contour of your mouth reduces the depth of the skin folds where saliva pools.
Breaking a lip-licking habit matters too. Saliva evaporates quickly and leaves the skin drier than before, creating a cycle of licking, drying, cracking, and licking again. Keeping a lip balm on hand gives you something to reach for instead. For people with confirmed nutrient deficiencies, maintaining adequate intake of iron, B vitamins, and protein through diet or supplementation addresses one of the most correctable root causes.