Why the corners of your mouth keep splitting, and what actually clears it
Angular cheilitis is usually candida or staph growing in a moist fold, so an occlusive can protect the skin but will not clear the infection underneath.
Splits at the corners of the mouth behave differently from ordinary chapped lips. They stay in one place, they crack open every time you yawn, and they get no better on the balm that fixes everything else. That pattern has a name, angular cheilitis, and a mechanism that explains why the usual response makes it last longer.
Corner cracks are usually a wet problem, not a dry one. Saliva pools in the fold, softens the thin skin there, and Candida albicans, Staphylococcus aureus or both colonise the damaged surface. A balm cannot clear an organism, and a thick occlusive over a damp fold preserves the conditions the organism prefers. Anything unresolved at two weeks belongs with a GP or dentist.
Why the damage sits exactly there
The oral commissure is the anatomical corner where the upper and lower lips meet, and it is the worst piece of real estate on the face for skin health. Three things converge on it. The skin is thin and it is folded, so two surfaces sit against each other with no air between them. The fold is the lowest point of the mouth's opening for most of the day and every night, so saliva collects there by gravity rather than by any fault of yours. And the tissue at the angle is a transition zone between lip vermilion and ordinary facial skin, so it has neither the mucosal defences of one nor the robust barrier of the other.
Skin that stays wet does not stay strong. Prolonged wetting causes maceration: the corneocytes swell, the lipid lamellae between them are disrupted, and the barrier that normally holds water in and keeps organisms out becomes soft, permeable and easy to tear. The architecture being disrupted is described in moisturisers and the skin barrier, and the important detail is that macerated skin fails mechanically. A fold that opens and closes several thousand times a day then fissures along the crease, and once there is a fissure there is a portal.
There is a chemical contribution as well. Saliva sits at roughly pH 6.7 to 7.4, while healthy skin surface sits nearer pH 4.7 to 5.5. Keeping a fold of skin at close to neutral pH suppresses the acid mantle that normally discourages colonisation, and it happens to be the condition under which Candida albicans switches most readily from a harmless yeast form to the invasive hyphal form. Saliva also carries amylase and lipase, digestive enzymes that are entirely appropriate on food and unhelpful on softened skin.
Maceration first, colonisation second
The sequence matters, because it explains why the problem does not clear on its own. Wetting damages the barrier, the damaged barrier is colonised, and the colonising organisms produce inflammation that keeps the tissue damaged. That loop is self sustaining once it has started, and removing only the original cause often is not enough.
Two organisms dominate the cultures. Candida albicans is a normal resident of the mouth in a large fraction of healthy people and only becomes a problem when the local environment favours it. Staphylococcus aureus arrives from the anterior nares, where roughly one adult in five carries it persistently and many more carry it intermittently, which is one reason nose to lip proximity matters here. One frequently cited Swedish clinical and microbiological series found staphylococci alone in about a fifth of cases, Candida alone in about a fifth, and both organisms together in the remainder, and mixed colonisation is a recurring theme in later work. In practice you cannot tell which you have by looking, which is a large part of why self treatment goes wrong.
There is usually a reservoir feeding the corners, too. In denture wearers the fitting surface of the appliance is the reservoir and the corners are the visible symptom, so clearing the corners without addressing the denture reliably produces a recurrence within weeks.
Why more balm can make it last longer
An occlusive film works by slowing water loss from the surface it covers. That is exactly what dry, cracked lip vermilion needs, and the physics of it are set out in occlusive, emollient and humectant. Applied to a fold that is already wet, the same film does something different: it traps moisture in, raises the hydration and the surface temperature of tissue that is already macerated, and holds a warm damp environment against a growing organism. Occlusion is a standard laboratory technique for encouraging skin hydration and, incidentally, for encouraging microbial growth on skin. It is not a neutral act.
Consistency compounds the error. A thick balm packed into the crease behaves like a plug rather than a film. It holds saliva against the skin instead of excluding it, and each reapplication adds material without removing what is underneath. People who report that their corner cracks improved when they stopped using anything are usually describing this effect rather than a cure.
Do not reach for an anti fungal, an antibiotic cream or a steroid cream left over from something else. Candida and staph need different treatment, a steroid used alone on a candidal infection typically makes it worse after an initial improvement, and topical antibiotics used speculatively drive resistance. Which organism is present is a diagnostic question, not a guessing game.
How it differs from ordinary chapping
The distinction is worth making carefully, because the two conditions look similar at a glance and respond to completely different things. Ordinary chapping is a barrier problem across a whole surface and it answers to protection. Angular cheilitis is a localised infected fold and it does not.
| Feature | Ordinary chapping | Angular cheilitis |
|---|---|---|
| Location | Across the whole vermilion, worst in the centre | Fixed at one or both angles, often triangular, spreading a few millimetres onto the skin |
| Surface | Flaking, scaling, sometimes a central split | Fissure along the crease, redness, crusting, sometimes a white or moist film |
| Symmetry | Symmetrical by nature | Often bilateral, but one side is commonly worse |
| Trigger | Cold, wind, dry indoor air, lip licking | Saliva pooling, denture fit, drooling, an underlying reservoir |
| Response to a bland balm | Clear improvement within days | Little or none, and sometimes worse under a thick layer |
| Course | Resolves and recurs with the weather | Persists for weeks, or clears and returns in the same spot |
| Pain | Tightness and stinging on the whole lip | Sharp pain on opening the mouth wide, bleeding at the angle |
If you are unsure which you are looking at, the response test settles most cases. Weather related chapping improves noticeably within three to five days on a plain occlusive used properly, and the realistic quantities are covered in how much balm to apply. A corner that has not changed at all in that period is not being caused by dryness.
The mechanical causes, which are the ones people miss
Anything that deepens the fold or increases the time saliva spends in it will produce this problem in an otherwise healthy person.
Lost vertical dimension. The height of the lower face is maintained by the teeth. Heavy tooth wear, missing back teeth, or dentures that have become too short over time all reduce that height, which over closes the bite and deepens the crease at the corners. This is the single most common mechanical cause in older adults, it is a dental assessment rather than a medical one, and no cream will correct it.
Denture fit and hygiene. Poorly fitting dentures both deepen the fold and provide a reservoir for Candida in the fitting surface. Dentures left in overnight are a recognised risk factor for oral candidiasis in general.
Orthodontic appliances. Fixed braces and aligners change lip posture, increase saliva production and make lip closure harder, which is why corner cracking is common in teenagers during treatment and often resolves when the appliance comes out.
Drooling and mouth breathing. Sleeping on your front or side with an open mouth soaks the lower corner for hours. Nasal obstruction, allergic rhinitis, sedating medication and anything that dries the mouth and prompts compensatory behaviour all feed into this, and the same overnight mechanism drives a lot of ordinary winter chapping, discussed in cold weather skin.
Lip licking and lip picking. The corners are the easiest place to reach with the tongue and the hardest to leave alone once they are sore. A flavoured or sweetened product actively encourages this, which is one of several reasons flavour and sweeteners are a bad idea on a lip that is already in trouble. In children, thumb sucking and dummy use do the same thing, and the wider picture for that age group is in lip balm for children.
Systemic contributors, kept in proportion
Nutritional deficiency is the explanation the internet reaches for first and the clinician reaches for last, which is roughly the correct order. In a well nourished adult with a new crack and an obvious mechanical cause, deficiency is unlikely. In someone with recurrent disease, no mechanical explanation, or other signs such as a sore smooth tongue, fatigue or pallor, it becomes worth investigating.
The associations that appear consistently in the literature are iron deficiency, riboflavin (vitamin B2), vitamin B12 and folate, and zinc. Riboflavin deficiency has been described with angular stomatitis and glossitis since the earliest nutritional work on the vitamin, though it is uncommon where dairy and fortified cereals are eaten. Beyond nutrition, poorly controlled diabetes raises the risk of candidal infection generally, immunosuppression from disease or medication does the same, and isotretinoin causes cheilitis in the large majority of people who take it, with the angles a frequent site. Inflammatory bowel disease can present with oral signs including angular fissuring.
Do not start iron or zinc supplements on the strength of a cracked lip corner. Iron in particular is harmful in excess and is dangerous to children who find the packet, and taking it before a blood test can obscure the result the clinician needs. If deficiency is genuinely on the table, the test comes first.
What clinicians actually use
This is an outline of the approach so you know what to expect, not a set of instructions, and the choice depends on an examination you cannot perform on yourself. If a clinician has already given you a regimen, theirs takes precedence over anything here.
Treatment usually has three parts. The organism is addressed with a topical antifungal where Candida is likely, an antibacterial where staphylococcus is implicated, or a combined preparation where both are suspected or where inflammation is marked, sometimes with a mild corticosteroid included to settle the inflammatory component. The reservoir is addressed at the same time, which may mean treating oral candidiasis, changing denture hygiene, or leaving dentures out overnight. And the mechanical cause is corrected, which is where a dentist rather than a doctor may be the person who actually resolves it.
One specific interaction is worth knowing about because the products involved are sold over the counter in some countries. Miconazole, a common topical antifungal, can potentiate warfarin and cause dangerous bleeding, which is why UK regulators contraindicated the oral gel form for people taking warfarin. Tell whoever is prescribing about anticoagulants and about every other medicine you take.
The one job a bland ointment can honestly do
There is a role for a simple product here, and it is narrow. A thin film of a bland, flavour free ointment at the angles before bed reduces the amount of time saliva spends in direct contact with damaged skin overnight, which is the longest uninterrupted exposure of the day. That is a barrier function, not a treatment, and it works alongside whatever a clinician has prescribed rather than instead of it.
What that product should be is unglamorous. Highly refined petrolatum is the usual first choice because it is the most effective occlusive available, has almost no capacity to sensitise, and is used as the standard vehicle in patch testing for that reason. A zinc oxide containing barrier ointment is the other sensible option, since zinc oxide adds a physical barrier and mild astringency in a fold that is too wet rather than too dry. What it should not contain is flavour, fragrance, menthol, camphor or a long botanical list, and the ingredient list is easy enough to check using the label reading method. The reasoning behind a short list on damaged lip tissue is set out in ingredients for chapped lips.
Apply it with a clean cotton bud, not a finger, and use a fresh bud each time. Fingers move organisms from the nose and mouth into the pot, and a jar of ointment that has been fingered while a staph infection is active becomes a reservoir of its own. The same hygiene logic applies to any open pot, and is worth a look in storing balms at home. Blot the corners dry first, then apply a film thin enough to see the skin through, rather than packing the crease.
A realistic timetable
| Day | What to do | What it tells you |
|---|---|---|
| 0 | Stop flavoured products, stop licking, blot the corners dry, thin bland film at night only | Removes the additions that most often prolong it |
| 3 | Reassess. Plain chapping should be visibly better by now | No change points away from simple dryness |
| 7 | Look for the mechanical cause: sleep position, nasal congestion, denture or brace, recent dental change | Finding one often explains recurrence as well as the current episode |
| 14 | Book a GP or dentist appointment if the fissures are still there | Two weeks without resolution means something is being maintained |
| 14 | Book regardless of appearance if this is the third episode in a year | Recurrence is the pattern that suggests a reservoir or a systemic cause |
Bring three things to that appointment: how long it has been going on, what you have already applied to it, and whether anything has changed with your teeth, dentures, medication or general health. Mention it to a dentist as readily as to a doctor, because the mechanical causes are dental and the dental examination is the one that finds them.
Red flags that do not wait two weeks
Get seen sooner if a crack bleeds repeatedly, if there is swelling or spreading redness onto the cheek, if a lesion is firm, raised or ulcerated rather than a simple fissure, if only one corner is affected and it has been present for weeks without change, if you are immunosuppressed or diabetic, or if the sore area is accompanied by white patches inside the mouth. Persistent one sided lesions on the lip in particular need a look from someone who can examine them, and a persistent rough or white patch anywhere on the lip that will not resolve is a reason to be seen rather than to buy another product. None of this is a diagnosis, and the limits of what any reference page can tell you are set out in the safety disclaimer.
The decision rule, and what a balm cannot do
Reduced to one line: if the crack is in the corner and it has not moved in a fortnight, the problem is not dryness and no change of product will settle it. Balms are cosmetics. They protect a surface, they slow water loss, and they have no antimicrobial function that a regulator would recognise, which is the boundary explained in cosmetic versus drug claims. Buying a more expensive, more natural or more heavily marketed one changes nothing about that boundary.
The honest limit of this page is that it cannot tell you which organism is in your fold, and that is the fact the treatment turns on. What it can do is stop you spending a month cycling through products, reframe the corners as a wet problem rather than a dry one, and identify the mechanical cause you may be able to fix yourself. Where a fungal organism is genuinely involved, incidentally, the reasoning about oils and yeasts is different for a different organism entirely, and the distinction between the two situations is worth understanding if you have read about malassezia safe balms. And if the balm you were using turns out to have been part of the problem, the wider version of that story is in does lip balm dry your lips.
Frequently asked questions
What causes cracked corners of the mouth?
Most often saliva pooling in the fold at the corner of the mouth, which softens the thin skin there until it fissures, followed by colonisation with Candida albicans, Staphylococcus aureus or both. Mechanical causes that deepen the fold are common, particularly lost tooth height, ill fitting dentures, braces, drooling overnight and lip licking. Nutritional deficiency and diabetes are less common contributors, mostly in recurrent cases.
Why does lip balm not fix the corners of my mouth?
Because a balm addresses dryness and the corners are usually too wet, not too dry. An occlusive film slows water loss, which helps chapped lip surfaces, but over a damp fold it traps moisture and warmth against skin that is already macerated and holds the environment the colonising organism prefers. A balm has no antimicrobial function, so it cannot clear the cause.
How long should cracked corners take to heal?
Simple chapping at the angles improves noticeably within three to five days of protecting it and stopping lip licking. Angular cheilitis usually does not. If the fissures are unchanged after two weeks of sensible care, or if you have had three episodes in a year, that is the point to see a GP or a dentist rather than to try another product.
Is angular cheilitis contagious?
The condition is not passed on the way a cold sore is, but the organisms involved are ordinary residents and can be spread by shared items. Do not share lip products, and avoid dipping fingers into a pot while an infection is active, because that turns the pot into a reservoir. Use a clean cotton bud for each application instead.
Does a vitamin deficiency cause cracks at the corners of the mouth?
It can, but it is not the usual cause in a well nourished adult. Iron, riboflavin, vitamin B12, folate and zinc deficiency are all associated with angular cheilitis, and are worth investigating when the problem keeps returning, when there is no mechanical explanation, or when there are other signs such as a sore tongue or fatigue. Get tested rather than supplementing speculatively.
Can I use an antifungal cream from the pharmacy?
That is a decision for a clinician, because Candida and staphylococcus require different treatment and the two cannot be told apart by looking. Steroid creams used alone on a candidal infection typically make it worse. One antifungal, miconazole, can interact dangerously with warfarin, so anyone on an anticoagulant should be particularly careful about self treating.
What should I put on cracked mouth corners overnight?
A thin film of a bland, flavour free ointment at the angles reduces how long saliva sits against damaged skin during the longest exposure of the day. Refined petrolatum or a zinc oxide barrier ointment are the usual choices. Apply with a clean cotton bud onto blotted dry skin, thin enough to see the skin through it. This protects; it does not treat the underlying infection.
Sources and further reading
- National Institute for Health and Care Excellence, Clinical Knowledge Summaries: Candida, oral, including the scenario covering angular cheilitis, NICE, United Kingdom.
- National Health Service, patient guidance on sore, cracked corners of the mouth and on oral thrush, NHS, United Kingdom.
- Medicines and Healthcare products Regulatory Agency, Drug Safety Update, guidance on the interaction between miconazole and warfarin, MHRA, 2016.
- Ohman and colleagues, clinical and microbiological study of angular cheilitis, Journal of Oral Pathology, 1986.
- Scully, Oral and Maxillofacial Medicine: the basis of diagnosis and treatment, Churchill Livingstone Elsevier, chapters on candidosis and lip disorders.
- US National Institutes of Health, Office of Dietary Supplements, Riboflavin fact sheet for health professionals.
- US National Institutes of Health, Office of Dietary Supplements, Iron fact sheet for health professionals.
Reviewed and updated 6 September 2026. Spotted an error? Tell us and we will fix and log it.