It starts with a tiny bit of tightness. You’re eating a sandwich or maybe just laughing at a joke, and suddenly—zap—a sharp, stinging rip at the corner of your lips. You look in the mirror and see it. A raw, red slit that looks like a paper cut but feels way worse.
Most people call it a cracked lip. Doctors usually call it angular cheilitis.
If you're searching for a cut on side of mouth how to heal, you've probably already realized that standard Chapstick isn't doing much. In fact, slathering on the wrong ointment might be making it worse. This isn't just "dry skin." It’s often a localized infection or a specific nutritional red flag that your body is waving at you.
Why the corner of your mouth keeps splitting
The anatomy of your mouth is actually kind of a design flaw for some of us.
When you breathe at night, or if you have a slight overbite, saliva pools in the corners of your lips. This is the "intertriginous" area. Saliva is full of digestive enzymes. When it sits there and dries, it breaks down the delicate skin barrier. This creates a warm, moist micro-climate.
Bacteria and fungi love this. Specifically, a yeast called Candida albicans—the same culprit behind thrush—moves into those tiny cracks and sets up shop. That’s why the cut won't close. Every time you open your mouth to talk, you re-tear the healing tissue, and the yeast keeps the edges from knitting back together.
It's frustrating. It's painful. Honestly, it’s kind of gross when it starts to crust over with that yellowish tint.
Is it a cold sore or angular cheilitis?
People mix these up constantly. A cold sore (herpes simplex virus) usually starts as a tingle or a group of small blisters. It can happen anywhere on the lip. Angular cheilitis is strictly confined to the "angles" or corners. If it's just one or both corners and there are no blisters, you’re likely dealing with a split, not a virus.
The "Secret" causes most people miss
Sometimes the cut on the side of your mouth isn't about saliva at all. It’s about what’s happening inside your bloodstream.
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Iron and B-vitamins are the heavy hitters here. If you’re low on Vitamin B12, Riboflavin (B2), or Iron, your skin loses its ability to repair itself quickly. I've seen cases where someone struggled with a split lip for months, only to have it vanish after a week of high-quality B-complex supplements.
Check your toothpaste too.
Sodium Lauryl Sulfate (SLS) is a foaming agent in most major brands like Crest or Colgate. For some, SLS is a massive irritant. It thins the oral mucosa. If you have a persistent cut, switching to an SLS-free brand like Sensodyne (the specific SLS-free versions) or Verve can be a game-changer.
Cut on side of mouth how to heal: The step-by-step protocol
You want it gone by tomorrow. That might not happen, but you can definitely stop the pain by tonight.
1. Stop licking it. Seriously. It’s the hardest habit to break because the area feels dry. But your saliva is literally acidic to your skin. Every time you lick that corner, you're feeding the yeast and dissolving the new skin cells trying to bridge the gap.
2. Use a barrier, but make it the right one. Plain white petrolatum (Vaseline) is your best friend. It doesn't have fragrances or flavors that irritate the wound. However, if the cut is red and "weepy," Vaseline might just trap the infection inside.
3. The OTC "Triple Threat" Method. If you suspect it’s fungal (which most are), try a tiny dab of over-the-counter antifungal cream. Look for Clotrimazole—the stuff usually sold for athlete's foot. Put a tiny bit on the corner of your mouth before bed. Top it with a layer of 1% Hydrocortisone cream to kill the inflammation, then seal it all in with Aquaphor or Vaseline.
4. Check your dentures or retainers. If your dental hardware doesn't fit right, your "vertical dimension" changes. This makes the skin fold over itself more, creating a deeper pocket for spit to hide. If you wear a night guard, soak it in a denture cleaner daily. Bacteria on your retainer can reinfect the corner of your mouth every single night.
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What the science says about healing times
According to a study published in the Journal of Oral and Maxillofacial Pathology, angular cheilitis usually resolves within 48 to 72 hours once the proper antifungal treatment is started.
If you’ve been treating it for a week and it’s still gaping open?
That's when you go to the doctor. It could be a staph infection (Staphylococcus aureus). Bacteria require different treatment than yeast. A doctor might prescribe Mupirocin, a powerful topical antibiotic that clears up bacterial splits almost overnight.
Dietary tweaks that actually help
Eat some red meat or lentils. Get those iron levels up.
A lot of people find that taking a Zinc supplement helps skin integrity, but don't overdo it. Just a standard multivitamin is often enough to cover the bases if the issue is nutritional.
Also, hydrate. It sounds cliché. It is cliché. But if your systemic hydration is low, your skin is less elastic. Elastic skin doesn't rip as easily when you yawn.
Common mistakes to avoid
- Avoid Neosporin. Many people are actually allergic to Neomycin, one of the ingredients in Neosporin. Using it on a cut can cause contact dermatitis, making the area redder and itchier than the original cut.
- No spicy foods. This is more for comfort. Acids from citrus or heat from peppers will burn the raw tissue and trigger more inflammation.
- Don't pick the scab. I know it's tempting. But that yellow crust is part of the "scaffolding" your body uses to heal. If you rip it off, you're resetting the clock.
When should you worry?
Most of the time, a cut on the side of the mouth is just an annoyance.
But if you notice the redness spreading across your cheek, or if you develop a fever, that’s a sign of cellulitis—a deeper skin infection. This is rare for a simple lip crack, but it happens, especially in people with weakened immune systems or diabetes. Diabetics are actually much more prone to these cuts because yeast thrives on the higher sugar levels in their saliva.
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If you are a smoker, healing will take twice as long. Nicotine constricts the tiny blood vessels in your face, starving the wound of the oxygen it needs to repair the collagen.
Actionable steps for immediate relief
To get that cut to close and stay closed, follow this specific routine for the next three days.
First, wash the area with a very mild, fragrance-free cleanser and pat it dry. Do not rub. Rubbing creates micro-tears.
Second, apply a thin layer of an antifungal cream (like Lotrimin) if the area is itchy or very red. If it's just a dry rip, skip to the next step.
Third, apply a heavy layer of a zinc-oxide based cream at night. Yes, the white diaper rash cream (like Desitin). Zinc oxide is a powerful skin protectant and has mild antimicrobial properties. It stays on the skin even if you drool a bit in your sleep, providing a physical shield against saliva.
Fourth, switch to a straw for 48 hours. This prevents you from stretching the corners of your mouth too wide when drinking and keeps liquids away from the wound.
Finally, take a look at your B-vitamin intake. If you haven't been eating well or are under a lot of stress, a B-complex supplement might be the missing piece to preventing this from coming back next month.
Stay consistent with the barrier cream. Even after it looks healed, keep using a bit of Vaseline on those corners for another few days to ensure the new skin is strong enough to handle the movement of your mouth.