Vitamin B6 Deficiency: Skin Rashes and Cracked Lips

One of the oldest and most reliable clues that the body is running short on vitamin B6 shows up on the face and lips. People notice a greasy, flaky, reddened rash around the nose, eyebrows, and hairline that looks and feels exactly like stubborn dandruff or seborrheic dermatitis — and at the same time the lips crack, the corners of the mouth split and sting, and the tongue turns sore and shiny. Doctors gave these signs old-fashioned names — cheilosis (cracked, scaling lips), angular stomatitis (raw, fissured mouth corners), and glossitis (a smooth, inflamed tongue). This page explains why a lack of B6 specifically irritates skin and the moist lining of the mouth, why those same signs are not proof of B6 deficiency on their own, and how the picture is sorted out and corrected.

Table of Contents

1. What It Looks and Feels Like
2. The Mechanism: Why Low B6 Hits Skin and Lips
3. Be Honest: Many Things Cause This Same Rash
4. Clues That Point Toward B6
5. What Drives Low B6 in the First Place
6. Getting Tested
7. Correcting Low B6 Safely
8. When to Seek Care / Red Flags
9. Key Research Papers
10. Connections
11. Featured Videos

What It Looks and Feels Like

The skin and mouth signs of B6 deficiency tend to arrive together, in a recognizable cluster, because they share the same underlying cause. The classic description, documented in careful human studies going back to the 1950s, is a seborrheic-dermatitis-like rash — a greasy, scaly, reddened eruption concentrated where the skin has the most oil glands:

• Around the nose and the folds beside it (the nasolabial folds) — flaky, slightly greasy redness that many people first treat as dry skin that won't clear up.
• The eyebrows, the skin between them, and the eyelids — scaling and redness that can look like persistent dandruff of the brows.
• The scalp and hairline — heavy, oily flaking that resembles ordinary dandruff but resists the usual shampoos.
• Behind and around the ears — cracking and scaling in the skin creases.

At the mouth, three overlapping signs show up. Cheilosis is the medical word for lips that become dry, reddened, cracked, and scaling, sometimes with painful vertical splits. Angular stomatitis (also called angular cheilitis or perlèche) is the raw, fissured, sometimes weeping sores that form at the corners of the mouth, where the skin folds and stays moist — these can sting when you eat anything salty or acidic and may crack open when you yawn or smile. And glossitis is a sore, swollen tongue that loses its normal rough surface and becomes smooth, shiny, and often a deeper red, sometimes burning enough to make eating uncomfortable.

People describe the whole picture as “my face won't stop flaking and my lips and mouth corners keep splitting no matter what I put on them.” The rash is usually not intensely itchy the way an allergic rash is — it is more greasy and scaly than maddeningly itchy — and the mouth signs are more painful than they look. A telltale feature is that ordinary moisturizers, lip balms, and dandruff shampoos help only a little and never fully clear it, because the problem is being driven from the inside out.

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The Mechanism: Why Low B6 Hits Skin and Lips

To understand why a lack of B6 lands on the skin and lips, it helps to know what B6 actually does. The active form of vitamin B6 in the body is pyridoxal 5′-phosphate (PLP). PLP is a coenzyme — a small helper molecule that an enzyme clamps onto in order to do its job. And it is not a minor helper: PLP is the cofactor for well over a hundred different enzymes, the great majority of them involved in handling amino acids, the building blocks of protein. PLP-dependent enzymes transfer, build, and break down amino acids; they help make heme (for red blood cells), several brain chemicals, and niacin from the amino acid tryptophan.

Now think about which tissues feel a protein-and-amino-acid bottleneck first. Skin, lips, the lining of the mouth, and the tongue are among the body's fastest-renewing tissues. Their surface cells are shed and replaced constantly, which means they are perpetually building new proteins — including keratin, the structural protein of skin and the protective barrier — and depend on a brisk, uninterrupted supply of amino-acid machinery. When PLP runs short, that machinery sputters. The amino-acid handling that fast-turnover tissues lean on is degraded, new skin and mucosal cells are built poorly, and the protective barrier becomes flaky, fragile, and prone to splitting. Laboratory work has shown that B6 (and the related vitamin riboflavin) is needed for the normal cross-linking and maturation of skin collagen, which is part of why deficiency leaves the skin's structure weakened.

An analogy. Picture the skin and lips as a busy bricklaying crew that never stops working — they are always tearing down old wall and laying fresh courses of brick. PLP is the mortar mixer that keeps the crew supplied. Slow-turnover tissues are like a finished building that needs only occasional patching; they can coast for a while on what they have. But the bricklayers who must lay a new course every single day notice the moment the mortar runs thin: the wall they put up is crumbly, the joints split, and the surface flakes. That is why a whole-body shortage of B6 announces itself loudest at the lips and the oil-rich skin of the face — the tissues with the highest day-to-day demand fail first.

The classic confirmation of this came from a deliberate human experiment. In 1950, researchers induced B6 deficiency in volunteers by combining a low-B6 diet with desoxypyridoxine, a compound that blocks B6, and watched a seborrheic-dermatitis-like rash and cheilosis develop — then watched both clear when B6 was given back. That cause-and-effect demonstration is why these skin and mouth signs are taught as the hallmark dermatologic features of B6 deficiency.

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Be Honest: Many Things Cause This Same Rash

Here is the part that matters most for a patient trying to make sense of their own skin: none of these signs is unique to vitamin B6 deficiency. A greasy facial rash, cracked lips, split mouth corners, and a sore tongue are some of the least specific findings in all of medicine. Far more often they have nothing to do with B6 at all. The honest list of common causes includes:

• Ordinary seborrheic dermatitis — an extremely common, chronic skin condition linked to a skin yeast (Malassezia) and the skin's oil. It produces exactly the same greasy, flaky rash on the scalp, brows, and nose folds in people whose B6 is perfectly normal. It is, by a wide margin, the most likely explanation for this rash.
• Other B-vitamin shortfalls — the skin and mouth signs of B6 deficiency overlap heavily with those of riboflavin (vitamin B2) deficiency — which classically causes its own cracked lips and mouth sores and facial rash — and with niacin (vitamin B3) deficiency, whose pellagra dermatitis and sore tongue can look similar. Because these B vitamins are often low together (a poor or alcohol-heavy diet shortchanges all of them at once), the clinical pictures blur.
• Iron deficiency — iron deficiency is a classic cause of angular stomatitis and a smooth, sore tongue (atrophic glossitis), and it is very common, especially in menstruating women.
• Zinc deficiency — low zinc produces a well-described rash around the mouth, nose, eyes, and in the groin, along with cracked mouth corners.
• Vitamin B12 and folate deficiency — either can cause a beefy, sore tongue and mouth changes.
• Local mouth-corner factors — angular cheilitis is frequently driven by mechanical and infectious factors that have nothing to do with diet: saliva pooling in deep skin folds (common with age, with dentures, or with significant weight loss), overgrowth of Candida yeast or staph bacteria, lip-licking habits, and contact reactions.

Because the overlap is so wide, a careful clinician treats this rash-and-lips picture as a prompt to look — not as a diagnosis in itself. The single biggest mistake a worried person can make is to assume a flaky face plus chapped lips “must be B6” and start high-dose pills. As covered below, too much B6 from supplements causes its own nerve problems, so guessing is not harmless.

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Clues That Point Toward B6

If the skin and lips are non-specific, what nudges the suspicion toward vitamin B6 in particular? A few patterns make B6 deficiency more plausible and are worth knowing:

• The rash won't respond to the usual skin treatments. A seborrheic-type rash that ignores antifungal/anti-dandruff shampoos and steroid creams — especially one that keeps coming back — should raise the question of a nutritional driver underneath it.
• It comes with the rest of the B6 picture. B6 deficiency rarely travels alone. When the rash and cracked lips arrive alongside the other legs of B6 deficiency — the tingling, burning, or numbness of nerve symptoms, the low mood and fog of depression and confusion, or the anemia and (in infants) seizures — the combination is far more suggestive than the rash by itself.
• There is a reason for low B6. The clinical context matters enormously. A person taking the tuberculosis drug isoniazid, which directly inactivates B6, who develops a seborrheic-type rash and cheilosis has a very B6-specific story — this drug-induced deficiency is so well established that B6 is routinely co-prescribed with isoniazid to prevent it. Heavy alcohol use, certain other medications, kidney dialysis, and malabsorption are other contexts (see the next section).
• It improves when B6 is restored. Ultimately, the most convincing clue is that the skin and lips heal once B6 status is corrected and the cause is fixed — just as they did in the controlled human studies.

Even with these clues, B6 deficiency is confirmed by putting the clinical picture together with the right context and, where appropriate, a blood level — not by the appearance of the skin alone. And because riboflavin and other shortfalls so often coexist, finding low B6 does not rule out that something else needs correcting too.

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What Drives Low B6 in the First Place

Outright vitamin B6 deficiency severe enough to cause a rash is uncommon in healthy people eating an ordinary mixed diet, because B6 is widely distributed in food — fish, poultry, organ and other meats, starchy vegetables like potatoes, bananas, chickpeas and other legumes, and fortified cereals all supply it. When deficiency does occur, it is usually because something is interfering with intake, absorption, or the vitamin's activity:

• Medications that inactivate B6. This is one of the most important and avoidable causes. Isoniazid (for tuberculosis) and the related drug cycloserine, the Parkinson's drug carbidopa/levodopa, the chelating agent penicillamine, and certain others chemically tie up B6 or its active form. Isoniazid in particular is a textbook cause of B6-deficiency rash, cheilosis, and nerve symptoms, which is why supplemental B6 is given alongside it.
• Heavy alcohol use. Alcohol both displaces B6-rich food from the diet and accelerates the breakdown of PLP, so chronic drinking is a leading cause of B6 deficiency — and, because it depletes riboflavin, niacin, and folate at the same time, it produces exactly the mixed skin-and-mouth picture that is so hard to pin on one nutrient.
• Malabsorption. Celiac disease, inflammatory bowel disease, and other conditions that impair nutrient absorption can lower B6 along with other vitamins.
• Kidney disease and dialysis. People on hemodialysis lose water-soluble vitamins, including B6, into the dialysate and frequently need supplementation.
• Poor overall diet. Diets very low in protein and variety — sometimes seen in frail older adults, in poverty, or in restrictive eating — can fall short of B6 along with the other B vitamins.

The reason the cause matters is the same as for the diagnosis: fixing a flaky face is temporary if the diuretic that caused it, the alcohol that drives it, or the isoniazid that ties up the vitamin is left unaddressed.

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Getting Tested

Vitamin B6 status is most directly assessed with a plasma pyridoxal 5′-phosphate (PLP) level — a blood test that measures the active form of the vitamin and is the most widely used and accepted marker of B6 status. A clinician interprets it in the context of the whole picture, because PLP can be lowered by inflammation independently of how much B6 someone is actually consuming.

Because the skin and mouth signs overlap so much with other deficiencies, testing rarely stops at B6. A sensible work-up usually looks for the common culprits as well: a complete blood count and iron studies (since iron deficiency is a far more frequent cause of angular stomatitis and a sore tongue), and often vitamin B12, folate, riboflavin, and zinc, depending on the history. A comprehensive metabolic panel checks kidney and liver function and helps frame the overall nutritional and medical context. If the mouth corners are weepy or crusted, a clinician may also swab for Candida or staph, because those frequently complicate or even fully explain angular cheilitis.

The practical point is that a single inexpensive round of bloodwork can both check B6 and, just as importantly, catch the iron, B12, or folate problem that is statistically more likely to be behind the same rash and cracked lips.

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Correcting Low B6 Safely

When low B6 is genuinely the driver, correcting it is straightforward, and the skin and lip signs typically improve over days to a few weeks once the vitamin is restored and the underlying cause is dealt with.

• Food first, for mild shortfalls. The adult Recommended Dietary Allowance for B6 is modest — about 1.3 mg/day for most adults, rising to 1.5–1.7 mg in older adults and 1.9–2.0 mg in pregnancy and breastfeeding. That is easily met by B6-rich whole foods: fish such as tuna and salmon, poultry and other meats, chickpeas and other legumes, potatoes, and bananas. See the Vitamin B6 food sources page for more. Building B6 in through ordinary food carries no risk of overshoot.
• Oral supplements, when needed. When diet alone isn't enough — or when an ongoing cause such as isoniazid, alcohol use, or dialysis keeps draining B6 — a clinician may prescribe a B6 supplement, often as part of a B-complex so the commonly co-existing riboflavin, niacin, and folate shortfalls are covered at the same time. Replacement doses for deficiency are typically modest and time-limited.
• Co-prescribe with the drugs that cause it. People starting isoniazid are routinely given supplemental B6 precisely to prevent the rash and nerve symptoms in the first place — a good example of fixing the cause rather than chasing the symptom.
• Treat the lips and mouth locally too. While B6 is being restored, gentle lip protection and, where a yeast or bacterial infection has set in, an antifungal or antibacterial cream for the mouth corners speeds healing of angular cheilitis.

An important caution that cuts the other way: more B6 is not better. Vitamin B6 is the one B vitamin with a well-established toxicity from supplements — chronic high doses (typically grams per day, but reported at lower doses over long periods) can cause a sensory peripheral neuropathy, with numbness, tingling, and unsteadiness, that is the mirror image of the deficiency's nerve effects. For that reason, an adult upper intake limit of 100 mg/day is set for B6 from supplements, and self-treating a flaky face with high-dose B6 — especially without confirming the vitamin is actually low — can do harm. Replacement should be guided by a clinician and the dose kept appropriate.

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When to Seek Care / Red Flags

A flaky face and chapped lips are rarely an emergency, and most cases are mild and treatable. But certain features mean the skin and mouth signs deserve prompt medical attention rather than another trip to the pharmacy:

• A rash or mouth sores that won't heal despite ordinary skin care, lip protection, and antifungal/anti-dandruff treatment — especially if it keeps recurring — warrants a work-up for a nutritional or medical cause.
• The skin signs come with neurological symptoms — new numbness, tingling, burning feet, weakness, unsteadiness, confusion, or (in an infant) seizures. That combination points to a more significant B6 problem (or its differential) and should be evaluated.
• You take isoniazid, cycloserine, penicillamine, or levodopa/carbidopa and develop a new rash, cracked lips, or nerve symptoms — tell your prescriber, because these drugs cause B6 deficiency and the dose of protective B6 may need adjusting.
• Signs of a different, treatable deficiency or infection — heavy fatigue, breathlessness, or pallor (suggesting iron-deficiency anemia), or mouth-corner sores that become red, crusted, swollen, or spreading (suggesting a Candida or bacterial infection that needs targeted treatment).
• You are already taking high-dose B6 and notice new numbness or tingling in the hands or feet — this can be a sign of B6 toxicity and the supplement should be stopped and the situation reviewed.

The unifying message is balance: a persistent flaky-face-and-cracked-lips picture is worth investigating because it can flag a fixable deficiency — but the fix is a confirmed diagnosis and a sensible dose, never a guess at high-dose pills.

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Key Research Papers

1. Mueller JF, Vilter RW (1950). Pyridoxine deficiency in human beings induced with desoxypyridoxine. Journal of Clinical Investigation;29(2):193-201. — DOI: 10.1172/jci102246
2. Vitamin B6 and Seborrheic Dermatitis in Man (1952). Nutrition Reviews;10(11):323-325. — DOI: 10.1111/j.1753-4887.1952.tb01034.x
3. Vitamin B6 Deficiency Following Isoniazid Therapy (1968). Nutrition Reviews;26(10):306-308. — DOI: 10.1111/j.1753-4887.1968.tb00828.x
4. Ink SL, Henderson LM (1984). Vitamin B6 Metabolism. Annual Review of Nutrition;4:455-470. — DOI: 10.1146/annurev.nutr.4.1.455
5. Percudani R, Peracchi A (2003). A genomic overview of pyridoxal-phosphate-dependent enzymes. EMBO Reports;4(9):850-854. — DOI: 10.1038/sj.embor.embor914
6. Ueland PM, Ulvik A, Rios-Avila L, et al. (2015). Direct and Functional Biomarkers of Vitamin B6 Status. Annual Review of Nutrition;35:33-70. — DOI: 10.1146/annurev-nutr-071714-034330
7. Bjørke-Monsen AL, Ueland PM (2023). Vitamin B6: a scoping review for Nordic Nutrition Recommendations 2023. Food & Nutrition Research;67. — DOI: 10.29219/fnr.v67.10259
8. Powers HJ (2003). Riboflavin (vitamin B-2) and health. American Journal of Clinical Nutrition;77(6):1352-1360. — DOI: 10.1093/ajcn/77.6.1352
9. Hegyi J, Schwartz RA, Hegyi V (2003). Pellagra: dermatitis, dementia, and diarrhea. International Journal of Dermatology;43(1):1-5. — DOI: 10.1111/j.1365-4632.2004.01959.x
10. Heath ML, Sidbury R (2006). Cutaneous manifestations of nutritional deficiency. Current Opinion in Pediatrics;18(4):417-422. — DOI: 10.1097/01.mop.0000236392.87203.cc
11. Lekwuttikarn R, Teng JMC (2018). Cutaneous manifestations of nutritional deficiency. Current Opinion in Pediatrics;30(4):505-513. — DOI: 10.1097/mop.0000000000000652
12. Tucker HA (1976). Acquired Zinc Deficiency. JAMA;235(22):2399. — DOI: 10.1001/jama.1976.03260480019022

PubMed Topic Searches

• PubMed — Vitamin B6 deficiency and seborrheic dermatitis
• PubMed — B6 deficiency: cheilosis, angular stomatitis, glossitis
• PubMed — Isoniazid, pyridoxine deficiency, and dermatitis
• PubMed — Angular cheilitis: iron and riboflavin causes
• PubMed — Pyridoxal 5′-phosphate and amino-acid metabolism

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Connections

• Vitamin B6 Deficiency Hub
• B6 Deficiency: Nerve Symptoms
• B6 Deficiency: Depression & Confusion
• B6 Deficiency: Anemia & Seizures
• Vitamin B6 Overview
• Vitamin B6 Food Sources
• Vitamin B6 Benefits
• Riboflavin (B2) Deficiency: Skin Rashes
• Riboflavin (B2): Cracked Lips & Mouth Sores
• Niacin (B3) Deficiency: Dermatitis
• Riboflavin (Vitamin B2)
• Niacin (Vitamin B3)
• Iron Deficiency
• Zinc
• Complete Blood Count
• Comprehensive Metabolic Panel
• Tuna
• Chickpeas
• Bananas

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