Cracked lips (angular cheilitis)

Cracked lips and cracked, sore corners of the mouth are extremely common and most of the time have simple causes: cold or dry weather, dehydration, sun, wind, habitual lip-licking, mouth-breathing, or an allergic or irritant reaction to a cosmetic or toothpaste. Cracks specifically at the corners of the mouth (angular cheilitis) often involve a build-up of moisture and infection there — commonly with the yeast Candida or with bacteria — and are more likely in people who wear dentures, have deep skin folds at the mouth, or dribble saliva. Beyond these everyday causes, persistent or recurrent cracking, particularly at the corners, can be a sign of nutritional shortage: deficiencies of riboflavin (B2), niacin (B3), pyridoxine (B6), folate, vitamin B12 or iron classically produce sore corners of the mouth alongside a sore tongue and other mouth changes. It can also accompany conditions that affect the immune system or skin, and is more common in people with diabetes (who are more prone to yeast). So while occasional cracked lips are trivial, cracks that keep coming back or won't heal — especially with a sore tongue, tiredness or a poor diet — are worth looking into.

• Dry or cold weather, sun and wind — the commonest cause.
• Dehydration and lip-licking or mouth-breathing.
• Angular cheilitis — infection (often yeast) at the corners, common with dentures or deep mouth folds.
• B-vitamin deficiencies — riboflavin (B2), niacin (B3), B6, folate or B12.
• Iron deficiency.
• Diabetes — more prone to yeast infection at the corners.
• Irritant or allergic reaction — to lip products or toothpaste.

• Iron studies (ferritin, iron) — for iron deficiency, a classic cause of angular cheilitis.
• B vitamins (B2, B6, B12, folate) — deficiencies produce sore mouth corners and tongue.
• Blood count — for associated anaemia.
• Glucose / HbA1c — if diabetes is suspected (predisposes to yeast).
• The rest is usually clinical — examining the lips and mouth, and reviewing diet and denture use.