Medically reviewed guide · Last updated: 2 November 2026 · Reading time: approx. 9 min

Cracked Corners of the Mouth: Yeast, Deficiency or Saliva?

The most common causes compared

The causes in detail

The skin at the corners of the mouth is constantly on the move: when you talk, eat and laugh, it is stretched and folded again, and it borders directly on the moist mouth. If it becomes too moist or too dry, it cracks easily. Doctors then speak of angular cheilitis, an inflammation of the corner of the mouth. Almost always several factors work together: a cause that weakens the skin, and germs that settle in the cracks.

This article covers cracks on the outside of the corner of the mouth. Painful, roundish sores inside on the lining of the mouth are usually aphthous ulcers — there is a separate article on mouth ulcers. Tingling blisters on the lip that crust over point more towards cold sores, described under herpes.

Saliva and moisture: the “damp chamber”

With age, the skin loses its elasticity, the corners of the mouth droop, and deep folds form in which saliva collects. Worn or poorly fitting dentures make this worse, because the bite height decreases and the corners of the mouth fold in more. In younger people, frequent lip licking, thumb sucking, fixed braces, drooling during sleep or wearing a mask for long periods are typical triggers. The skin softens, cracks, and the cycle begins: it feels tight, you moisten your lips, it cracks further. First step: keep the corners of your mouth dry and protect them with a greasy barrier, such as petroleum jelly or a zinc ointment, especially overnight. If you wear dentures, an appointment at your dental practice to check the fit and bite height is worthwhile.

Yeasts: when the cracks will not heal

The yeast Candida albicans lives unnoticed in the mouths of many people. In moist mouth corners it finds ideal conditions. Typical are reddened cracks, sometimes with a whitish coating, that do not heal despite care or keep coming back. A yeast infection is encouraged by dentures, especially if they are worn at night, by poorly controlled diabetes, after antibiotics, with inhaled cortisone and with a weakened immune system. The yeast often also shows up in the mouth as a white coating that can be wiped off (oral thrush) or as reddened lining under the dentures. First step: have a doctor check whether yeast is involved; antifungal creams then usually help. The dentures need to be treated as well, otherwise the infection comes back.

Bacteria: honey-yellow crusts

Staphylococcus aureus and streptococci can also settle in cracked mouth corners, alone or together with Candida. Typical are weeping areas with honey-yellow crusts that can spread to the surrounding skin. This is seen more often in children and in people with atopic dermatitis, whose skin barrier is already disturbed. First step: show it to your GP or paediatric practice; treatment is usually with antiseptic or antibiotic creams, and with extensive infection also with tablets.

A lack of iron, B vitamins or zinc

Cracked mouth corners are considered a classic sign of a nutrient deficiency — but in Germany, a deficiency is the sole cause less often than is commonly assumed. The most likely candidate is iron deficiency, for example with heavy periods, during pregnancy or with unnoticed blood loss; background in the guide Iron deficiency. A vitamin B12 deficiency or folic acid deficiency often also causes a smooth, red, burning tongue, tiredness and sometimes tingling in the hands and feet. A lack of vitamin B2 (riboflavin), B6 or zinc can also make the corners of the mouth crack. People at risk include those with a one-sided diet, high alcohol consumption, bowel diseases such as coeliac disease or Crohn's disease, and those on a vegan diet without B12 supplements. First step: have a blood count, ferritin (iron stores), vitamin B12 and folic acid measured at your GP practice instead of taking supplements on suspicion.

Dry skin, eczema and contact allergies

Cold, wind and dry heated air dry out the lips and corners of the mouth. With dry skin and atopic dermatitis, the skin cracks more quickly and itches. Sometimes the skin reacts allergically to ingredients in toothpaste, mouthwash, lip balm or cosmetics, such as fragrances, or to metals. Then a wider area around the mouth is usually red and scaly. First step: leave out new products and use fragrance-free, moisturising care; if an allergy is suspected, a patch test at a dermatology practice will help.

When the mouth is too dry or the immune system is weakened

Paradoxically, too little saliva also encourages cracked mouth corners: with dry mouth, the protection provided by saliva is missing, yeasts multiply more easily, and you moisten your lips with your tongue more often. Sjögren's syndrome, which dries out the mouth and eyes, can be behind it. With a weakened immune system — for example during chemotherapy, with strong immunosuppressants or with an untreated HIV infection — yeast infections in the mouth occur more often and are more pronounced and more stubborn. Recurring, extensive oral thrush without an obvious cause is therefore a reason for a thorough medical assessment.

Self-tests: first clues at home

These observations do not replace a diagnosis or a swab. But they help you narrow down the likely cause and report precisely at your appointment.

• The mirror check outside: a whitish coating on reddened cracks points more towards yeast, honey-yellow crusts more towards bacteria. A softened, moist fold at the corner of the mouth without a coating points to saliva as the main cause.
• The mirror check inside: look at your tongue, the lining of your cheeks and the roof of your mouth. White patches that can be wiped off and are red underneath fit oral thrush. A smooth, red, burning tongue can point to iron or B12 deficiency.
• The habit check: do you often lick your lips? Do you wake up with a damp pillow? Do you wear your dentures at night? An honest yes is often half the explanation.
• The denture check: are your dentures loose, do they press, or are they more than a few years old? Is the lining underneath reddened? Then your dental practice needs to be involved.
• The accompanying signs check: tiredness, paleness, brittle nails, hair loss, tingling in the feet, severe thirst or frequent urination? Then your blood values and blood sugar should be checked.
• The two-week test: keep the corners of your mouth dry and protect them consistently with a greasy barrier. If the cracks do not clearly heal within about two weeks, an infection or another cause is likely.

Warning signs: when not to wait

• A sore, crust or hardened area on the lip or corner of the mouth that has not healed after about three weeks, keeps bleeding or feels hard — especially in smokers and after a lot of sun
• Extensive white patches in the mouth with pain when swallowing or the feeling that food gets stuck
• Sore mouth corners and an inflamed lining of the mouth while taking methotrexate or during chemotherapy
• Marked paleness, breathlessness on exertion, a racing heart, numbness or tingling in the hands and feet
• Severe thirst, frequent urination or unintentional weight loss
• Redness and swelling that spread rapidly over the lip and face, with fever
• Oral thrush that keeps coming back without an obvious cause

The treatment pathway: step by step

1. Keep dry and protect. Gently pat the corners of your mouth dry after eating and drinking, do not lick your lips, apply a greasy barrier such as petroleum jelly or zinc ointment, especially before going to sleep.
2. Remove the triggers. Pause new cosmetics and toothpaste, take your dentures out at night and clean them thoroughly every day, rinse your mouth after inhaling cortisone.
3. Have it checked by a doctor if the cracks have not healed after about two weeks, keep coming back, or are coated or crusted. Your GP or dermatology practice can take a swab and measure blood values: blood count, ferritin, vitamin B12, folic acid and, depending on the situation, blood sugar.
4. Targeted treatment. For a yeast infection, antifungal creams, for example with clotrimazole, nystatin or miconazole; for bacteria, antiseptic or antibiotic creams. With severe inflammation, the practice sometimes prescribes a combination with a mild cortisone for a short time. A proven deficiency is corrected in a targeted way.
5. Treat the cause as well. New or relined dentures if the bite height has decreased, better control of diabetes, a search for the cause of a deficiency. In stubborn cases, a dermatology practice follows, and rarely a tissue sample.
6. Which treatment is right is always decided by the practice treating you, together with you — especially if you take blood thinners or other long-term medicines.

The medication angle: when active substances affect the corners of the mouth

Isotretinoin: cracked lips as the rule

With isotretinoin for severe acne, dry, cracked lips and mouth corners are a very common side effect according to the summary of product characteristics. Consistent lip care from the start is therefore part of the treatment. If the cracks become deep, weeping or coated, the practice treating you should check whether an infection has developed on top.

Cortisone inhalers and antibiotics: paving the way for yeasts

Inhaled cortisone such as budesonide or fluticasone for asthma or COPD can encourage oral thrush and sore mouth corners if traces of the active substance remain in the mouth. The simple countermeasure: rinse your mouth or eat something after inhaling; a spacer further reduces the amount in the mouth. How to do this is shown in the guide Inhaling correctly. So you should not stop the inhaler because of this. Antibiotics, too, disturb the natural flora of the mouth and clear the way for Candida.

Medicines that dry out the mouth or dampen the immune system

Medicines with anticholinergic effects, such as tricyclic antidepressants, bladder medicines or some Parkinson's medicines, reduce the flow of saliva. Immunosuppressants, cortisone tablets and chemotherapies weaken the defences against yeasts; some cancer medicines also cause an inflammation of the lining of the mouth (mucositis). With methotrexate, a sore lining of the mouth is a warning sign (see warning signs).

Active substances that deplete nutrients

Metformin can reduce the absorption of vitamin B12 when taken for a long time, as can years of treatment with acid blockers such as pantoprazole. With long-term use, your practice can therefore check your B12 level. You should not stop these medicines because of this — the deficiency can be corrected in a targeted way.

Antifungals: watch out for interactions

If oral thrush is also being treated, miconazole as an oral gel is often an option. Part of it gets into the body and, according to the summary of product characteristics, it can considerably increase the effect of coumarin-type anticoagulants such as phenprocoumon — with a risk of bleeding. There are also relevant interactions with certain statins such as simvastatin and other active substances. So tell your practice and pharmacy which medicines you take, and check your combination in the interaction check. Tablets such as fluconazole are only prescribed for extensive infection and also have numerous interactions.

Painkillers: rarely needed

Cracked mouth corners burn, but rarely need painkillers. If they do, without medical advice you should usually take over-the-counter medicines such as ibuprofen or paracetamol for no longer than three to four days in a row. More in the painkiller comparison.

How to prevent cracked mouth corners

• Do not lick your lips — keep a fragrance-free lip balm to hand instead, especially in cold and wind.
• Care for your dentures and have them checked — clean them daily, take them out at night, and have the fit and bite height checked regularly at your dental practice.
• Rinse after inhaling cortisone — or inhale before a meal so that no traces remain in your mouth.
• Eat a varied diet — with iron-rich foods, wholegrains and dairy products; on a vegan diet, supplement vitamin B12, with background in the guide Medications and a vegan diet.
• Keep an eye on your blood sugar — well-controlled diabetes lowers the risk of yeast infections.
• Protect overnight — if you drool a lot in your sleep, apply a thin layer of petroleum jelly or zinc ointment to the corners of your mouth in the evening.

Ointments, inhalers and tablets in view — with brite

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