Vitamin A Deficiency: Skin Problems (Hyperkeratosis)

When the body runs short of vitamin A, one of the earliest places it can show is the skin. The skin turns dry, rough, and scaly, and a distinctive rash of tiny hard bumps appears around the hair follicles — most often on the outer arms, the fronts of the thighs, the buttocks, and the shoulders. Run your hand over it and it feels like coarse sandpaper or the skin of a plucked goose; this is why it has long been called “toad skin” (phrynoderma, from the Greek phrynos, a toad). The medical name for the underlying process is follicular hyperkeratosis — an overgrowth of the protein keratin that plugs each follicle. This page explains why too little vitamin A makes skin behave this way, why the same-looking bumps have several other (more common) causes, when the picture genuinely points to vitamin A, and how it is corrected.

Table of Contents

1. What Vitamin A–Deficient Skin Looks and Feels Like
2. The Mechanism: Why Low Vitamin A Plugs the Follicles
3. Be Honest: Most “Sandpaper” Bumps Are Not Vitamin A
4. Clues That It Really Is Vitamin A
5. What Causes Vitamin A Deficiency
6. Getting Tested
7. Correcting It Safely
8. When to Seek Care / Red Flags
9. Key Research Papers
10. Connections
11. Featured Videos

What Vitamin A–Deficient Skin Looks and Feels Like

The skin changes of vitamin A deficiency have a recognizable signature, and they tend to arrive in a particular order. The first and most general change is simple dryness — doctors call it xerosis. The skin loses its suppleness, looks dull and flaky, and may itch. People often assume it is just winter weather, harsh soap, or aging skin, and reach for moisturizer that helps only a little.

The more telling change is the rash of follicular hyperkeratosis, the classic phrynoderma:

• Small, hard, raised bumps — each one centered on a hair follicle. They are usually skin-colored, grayish, or brownish, dome-shaped, and 1–5 mm across. A tiny coiled or curled-up hair is often trapped under the keratin plug at the top of each bump.
• A sandpaper or “goose-flesh” feel — running a palm over the area feels like coarse sandpaper, a nutmeg grater, or the pimpled skin of a plucked bird. This rough texture, present all the time rather than only when cold, is what gives the condition its “toad skin” nickname.
• A typical distribution — it favors the extensor (outer) surfaces: the outer upper arms and elbows, the fronts of the thighs and the knees, the buttocks, and the shoulders. In more advanced cases it spreads to the back, abdomen, and even the face. The palms and soles are spared.
• Color and pigment changes — the bumps can look darker than the surrounding skin, and the overall area may take on a dry, dusty, hyperpigmented appearance.

The rash is usually not itchy or painful in itself, although the underlying dryness can itch. It builds up slowly over weeks to months rather than erupting suddenly. Because vitamin A is needed across all the body's linings, the skin findings often travel with other clues: very dry eyes and difficulty seeing in dim light (see Night Blindness & Eye Damage), dry or brittle hair, ridged nails, and a tendency toward repeated infections (see Weakened Immunity & Infections). It is the combination — sandpaper skin plus dry eyes plus night blindness in someone with a reason to be deficient — that should raise suspicion, far more than the skin alone.

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The Mechanism: Why Low Vitamin A Plugs the Follicles

To understand the bumps you have to understand what vitamin A does for skin in the first place. Vitamin A's active form in tissues is retinoic acid, and retinoic acid is one of the body's master switches for telling cells how to mature — a process called differentiation. It works by entering the cell nucleus and binding to retinoic acid receptors (RARs), which then switch specific genes on or off. In the epidermis, those genes control how a young skin cell turns into a properly formed surface cell and exactly how much of the tough structural protein keratin it makes (Vollberg et al., 1992; Nagae et al., 1987).

Healthy skin is in a constant, orderly turnover. New cells are born in the deep basal layer, then climb toward the surface, filling with keratin and flattening as they go, until they form a thin, flexible, water-resistant outer shell and are shed. Vitamin A keeps this assembly line controlled: it tells cells to make the right keratins in the right amounts and to mature at the right pace. When retinoic acid is in short supply, that brake comes off. The cells lining the skin and the hair-follicle openings switch into a coarser program — they pile up extra keratin and turn into a dry, scaly, “horny” tissue. Pathologists call this squamous metaplasia and keratinization; in laboratory and animal studies, removing vitamin A drives exactly this excess keratin production, and restoring retinoic acid normalizes how the keratin and barrier proteins are made (Lützow-Holm et al., 1994; Nagae et al., 1987).

The hair follicle is where this shows up most dramatically. Each follicle is a tiny tube, and its lining is constantly shedding keratin. Without enough vitamin A, that lining over-produces keratin, the debris cannot escape, and a hard keratin plug builds up in the mouth of the follicle — trapping the developing hair beneath it and raising the characteristic bump. Multiply that across thousands of follicles and you get a field of sandpaper-rough papules. The widespread dryness comes from the same root: an epidermis making the wrong kind of surface cells holds water poorly and loses its smooth, supple barrier.

An analogy. Think of vitamin A as the foreman on the skin's production line, walking the floor and telling each worker, “make this much keratin, no more, and finish on schedule.” Lose the foreman and the line doesn't stop — it overproduces. Workers churn out crude, excess material and pile it up in the doorways (the follicles) until they clog. The fix is not to tear out the factory but to bring the foreman back: restore vitamin A and orderly production resumes, the doorways clear, and the skin smooths out over the following weeks. (This same biology is why prescription retinoids — vitamin A relatives — are used to treat keratinization disorders; see Katugampola & Finlay, 2005, and the Vitamin A and Skin / Cellular Differentiation page.)

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Be Honest: Most “Sandpaper” Bumps Are Not Vitamin A

Here is the part that is easy to get wrong, and that a careful health page has to say plainly: rough, bumpy, follicular skin is extremely common, and in well-fed populations it is almost never caused by a lack of vitamin A. The look of phrynoderma is not unique to vitamin A deficiency. Several far more common conditions produce nearly identical “chicken-skin” bumps, and confusing them with a vitamin deficiency leads people to take supplements they don't need — supplements that, with vitamin A, can themselves cause harm.

The most important look-alikes:

• Keratosis pilaris — by far the most common cause of follicular bumps. It is a benign, very common, often inherited condition affecting up to a third or more of people, especially in childhood and adolescence. It produces the same fine, rough, “sandpaper” papules on the outer upper arms, thighs, cheeks, and buttocks. It has nothing to do with diet or vitamin A, it is harmless, and it often improves with age. The overlap with phrynoderma is so close that vitamin A deficiency was historically over-diagnosed in people who simply had keratosis pilaris.
• Plain dry skin (xerosis) and eczema — cold weather, low humidity, over-washing, harsh soaps, and the skin barrier problems of eczema (atopic dermatitis) all produce rough, scaly, itchy skin that can be mistaken for a nutritional rash.
• Other deficiencies and barrier problems — phrynoderma-like rashes have also been linked to a lack of essential fatty acids and B-complex and vitamin E, not vitamin A alone. Several classic studies of patients with phrynoderma found the picture tied more closely to fat and vitamin E status than to vitamin A (Bhat & Belavady, 1967; Nadiger, 1980; Christiansen et al., 1988). In other words, “toad skin” is better thought of as a sign of general undernutrition than as a specific vitamin A reading.
• Common skin conditions — acne, psoriasis, and folliculitis (inflamed or infected follicles) can all be mistaken for vitamin-related bumps by a non-specialist.

The honest bottom line: a field of rough follicular bumps, on its own, is much more likely to be ordinary keratosis pilaris or dry skin than vitamin A deficiency. Vitamin A deficiency becomes a real consideration only when the skin is part of a bigger picture — which the next section lays out — and especially when a person has a genuine reason to be deficient.

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Clues That It Really Is Vitamin A

What separates true vitamin A deficiency from the everyday look-alikes is almost never the rash by itself — it is the company the rash keeps and the context it appears in. The picture points toward vitamin A when several of these line up:

• Eye symptoms alongside the skin. This is the single most useful clue. The eye is the most vitamin A–sensitive organ, and ocular signs usually appear with or before significant skin disease. Difficulty seeing in dim light or while driving at night (night blindness), persistently dry, gritty eyes, and foamy gray patches on the white of the eye (Bitot's spots) are red-flag companions. See Night Blindness & Eye Damage. Sandpaper skin plus trouble seeing at night is a far stronger signal than either alone.
• A genuine reason to be deficient. Vitamin A deficiency does not strike a well-nourished adult eating a varied diet out of the blue. It points to vitamin A when there is fat malabsorption (cystic fibrosis, celiac or Crohn's disease, chronic pancreatitis, cholestatic liver disease, or after bariatric/intestinal surgery), a very restricted diet, chronic alcohol use, or a setting of childhood undernutrition (see causes below). Vitamin A is fat-soluble, so anything that blocks fat absorption blocks vitamin A.
• Repeated infections and poor wound healing. Vitamin A is essential for the immune system and the linings of the gut and airways, so true deficiency tends to come with frequent respiratory or gut infections (see Weakened Immunity & Infections).
• The rash improves with treatment of the deficiency. A practical, after-the-fact clue: phrynoderma from true deficiency typically clears over weeks once vitamin A (and often essential fatty acids and other missing nutrients) are restored. Keratosis pilaris does not respond to vitamin A.
• It does not fit keratosis pilaris. Keratosis pilaris is usually lifelong, started in childhood, sits mainly on the outer arms and cheeks, and has no other symptoms. Bumps that are new in an adult, spreading widely, and accompanied by eye or general-health changes fit deficiency better than long-standing “chicken skin” does.

Even with these clues, the rash is suggestive, not diagnostic. The way to settle it is to look at the eyes, take a careful diet-and-malabsorption history, and — where indicated — check a blood level, as described next.

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What Causes Vitamin A Deficiency

Globally, vitamin A deficiency is one of the most common and serious nutritional deficiencies in children in low-income regions, where it is a leading cause of preventable childhood blindness and raises the risk of death from infection. Large surveys still find substantial childhood deficiency in parts of South Asia and sub-Saharan Africa (Kundu et al., 2021). In wealthy countries it is uncommon in the general population but turns up reliably in a few situations:

• Fat malabsorption. Because vitamin A rides into the body with dietary fat, any disease that impairs fat absorption causes it: cystic fibrosis, celiac disease and Crohn's disease, chronic pancreatitis, cholestatic liver and biliary disease, and the aftermath of bariatric or extensive intestinal surgery. This is the leading cause in developed countries.
• Very limited or unbalanced diets. Diets low in both preformed vitamin A (liver, dairy, eggs, fish) and in colorful fruits and vegetables that supply provitamin A carotenoids (the orange and dark-green produce that the body converts to vitamin A). Severe poverty, food insecurity, extremely restrictive eating, and some highly selective eating patterns in children can get there.
• Chronic, heavy alcohol use. Alcohol both displaces good nutrition and interferes with how the liver stores and handles vitamin A, depleting the body's reserves over time.
• Liver disease. The liver is the body's vitamin A warehouse (storing it mostly as retinyl esters). Significant liver disease impairs both storage and the proteins that carry vitamin A in the blood.
• Infections in already-marginal children. Illnesses such as measles, persistent diarrhea, and intestinal parasites (a documented case tied phrynoderma to chronic giardiasis — Girard et al., 2006) sharply increase vitamin A use and loss, tipping a borderline child into overt deficiency. This is why the World Health Organization recommends vitamin A supplementation for children with measles in deficient settings.
• Increased need. Pregnancy and breastfeeding raise requirements, and a deficient mother both develops symptoms (classically night blindness in late pregnancy) and passes low stores to her infant.

Knowing the cause matters because the fix differs: a person with malabsorption needs the underlying gut or liver problem managed and often higher, monitored doses, whereas a child with a poor diet may need a simple food and supplement program — and an alcohol-related case will not improve durably without addressing the alcohol use.

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Getting Tested

Vitamin A deficiency is diagnosed by putting the clinical picture together with, when needed, a blood test — not by the rash alone. The steps a clinician takes:

• History and examination first. The diet, any malabsorption condition, alcohol use, and a look at the eyes (night-vision questions, dry-eye and Bitot's-spot check) often point to the answer before any blood is drawn. In children in deficient regions, the eye exam plus history is frequently the basis for treatment.
• Serum retinol. The standard blood test measures serum retinol, the circulating form of vitamin A. A level below roughly 0.70 µmol/L (about 20 µg/dL) indicates deficiency, and below about 0.35 µmol/L indicates severe deficiency. One important caveat: the liver buffers serum retinol tightly, so the blood level can stay near-normal until stores are quite depleted, and it also falls temporarily during any acute infection or inflammation (because the carrier protein drops). For that reason a single borderline result is interpreted alongside the whole picture, sometimes with an inflammatory marker like CRP to flag a falsely low reading.
• Retinol-binding protein (RBP). Vitamin A travels in blood bound to retinol-binding protein; measuring RBP is a cheaper, more field-friendly proxy used in some settings.
• Tests for the cause. When deficiency is confirmed or strongly suspected, the search shifts to why: liver function tests, markers of fat malabsorption and the conditions that cause it, and checks of the other fat-soluble vitamins (D, E, and K), which are commonly low together when fat absorption is the problem.
• Skin biopsy is rarely needed. Phrynoderma can be confirmed on biopsy (it shows the keratin-plugged follicles), but in practice the diagnosis is clinical and a biopsy is reserved for genuinely unclear cases.

For most patients in well-nourished countries presenting only with rough, bumpy skin and no eye symptoms or malabsorption, the right first step is usually a dermatology assessment to confirm ordinary keratosis pilaris — not a battery of vitamin tests.

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Correcting It Safely

If the skin changes are truly from vitamin A deficiency, the encouraging news is that they reverse: as retinoic acid signaling is restored, the epidermis returns to orderly keratin production, the follicular plugs clear, and the dryness and bumps fade over weeks to a couple of months. How it is done depends on the cause and severity, and — because vitamin A can be toxic in excess — it should be guided by a clinician, especially in pregnancy.

• Food first, in mild dietary cases. The adult RDA for vitamin A is about 900 µg RAE/day for men and 700 µg RAE/day for women. Two food routes supply it. Preformed vitamin A (retinol) is found in liver, cod liver and its oil, eggs, and dairy. Provitamin A carotenoids (mainly beta-carotene), which the body converts as needed, come from deeply colored produce: sweet potatoes, carrots, pumpkin, and dark leafy greens such as spinach and kale. A useful safety point is that beta-carotene from food does not cause vitamin A toxicity — the body simply slows its conversion when stores are full — so plant sources are a low-risk way to rebuild status. See the Vitamin A food sources page for amounts.
• Supplements / medical dosing for true deficiency. Confirmed deficiency, and any case with eye involvement, is treated with measured vitamin A under medical supervision. The WHO uses high-dose oral vitamin A protocols for deficiency and for children with measles or xerophthalmia in at-risk regions; these specific high doses are deliberate, short-course, and supervised — not something to copy from a bottle at home.
• Fix the underlying cause. In malabsorption, the gut or liver condition must be managed and a water-miscible form of vitamin A or higher doses may be needed because ordinary absorption is impaired. In alcohol-related deficiency, the alcohol use has to be addressed. Replacing the vitamin without treating the cause only buys time.
• Replace the fellow-travelers. Because phrynoderma so often reflects broader undernutrition, correcting it frequently means restoring essential fatty acids (from fish, nuts, and seeds; see omega-3 fatty acids), B-complex vitamins, vitamin E, and overall calories and protein — not vitamin A in isolation. Classic phrynoderma studies improved with combined nutritional repletion (Bhat & Belavady, 1967; Nadiger, 1980).
• Topical care for the skin itself. While stores rebuild, gentle skin care helps the texture: bland emollients, mild non-soap cleansers, and (for the bumps) keratolytics such as urea, lactic acid, or salicylic acid that soften the keratin plugs. Prescription topical retinoids can help keratinization disorders, but for simple keratosis pilaris these measures — not oral vitamin A — are the right approach.

An essential caution on the other direction. Vitamin A is fat-soluble and stored in the liver, so taking too much preformed vitamin A (from high-dose supplements, not from food carotenoids) is itself harmful — it can cause hair loss, dry cracking skin and lips, headaches, liver damage, and, critically, birth defects in pregnancy. This is exactly why self-treating sandpaper skin with megadoses of vitamin A is a bad idea: most such skin is not deficiency in the first place, and the “cure” can cause real injury. Doses for genuine deficiency are chosen and monitored by a clinician.

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When to Seek Care / Red Flags

Rough, bumpy skin by itself is rarely urgent and is usually benign keratosis pilaris. But get medical attention promptly — and think specifically about vitamin A — if the skin changes come with any of the following:

• Any eye symptoms — trouble seeing in dim light or while driving at night, persistently dry or gritty eyes, or foamy gray spots on the white of the eye. Vitamin A–related eye disease can progress to permanent corneal damage and blindness and needs urgent treatment.
• A known malabsorption condition — cystic fibrosis, celiac or Crohn's disease, chronic pancreatitis, cholestatic liver disease, or a history of bariatric/intestinal surgery, especially if other fat-soluble vitamins (D, E, K) are also low or you bruise and bleed easily.
• Signs of broader undernutrition — unintended weight loss, a very restricted diet, hair loss, brittle nails, or frequent infections and slow-healing wounds.
• A spreading, new rash in an adult — widespread, progressing follicular bumps that are new (rather than lifelong “chicken skin”), particularly with the features above.
• An infant or child in an at-risk setting, or any child with measles plus eye or skin changes — vitamin A deficiency in children is a medical priority because of the blindness and infection risks.
• Possible vitamin A excess — if you have been taking high-dose vitamin A supplements (or cod liver oil in large amounts) and develop dry cracked lips and skin, hair loss, headaches, bone or joint pain, or nausea, stop and seek advice; this is toxicity, not deficiency.

The recurring theme is that the skin is a clue, not a verdict. When the bumps stand alone in an otherwise healthy, well-fed person, reassurance and good skin care are usually all that is needed. When they travel with eye trouble, malabsorption, or undernutrition, that is when vitamin A deficiency moves from unlikely to likely — and when a quick clinical check and, if needed, a blood level are worth getting.

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Key Research Papers

1. Bhat KS, Belavady B (1967). Biochemical Studies in Phrynoderma (Follicular Hyperkeratosis). The American Journal of Clinical Nutrition;20(5):386-392. — DOI: 10.1093/ajcn/20.5.386
2. Nadiger HA (1980). Role of vitamin E in the aetiology of phrynoderma (follicular hyperkeratosis) and its interrelationship with B-complex vitamins. British Journal of Nutrition;44(3):211-214. — DOI: 10.1079/bjn19800033
3. Christiansen EN, Piyasena C, Bjørneboe GE, et al. (1988). Vitamin E deficiency in phrynoderma cases from Sri Lanka. The American Journal of Clinical Nutrition;47(2):253-255. — DOI: 10.1093/ajcn/47.2.253
4. Girard C, Dereure O, Blatière V, Guillot B, Bessis D (2006). Vitamin A Deficiency Phrynoderma Associated with Chronic Giardiasis. Pediatric Dermatology;23(4):346-349. — DOI: 10.1111/j.1525-1470.2006.00261.x
5. Vollberg TM, Nervi C, George MD, Fujimoto W, Krust A, Jetten AM (1992). Retinoic acid receptors as regulators of human epidermal keratinocyte differentiation. Molecular Endocrinology;6(5):667-676. — DOI: 10.1210/mend.6.5.1318502
6. Nagae S, Lichti U, De Luca LM, Yuspa SH (1987). Effect of Retinoic Acid on Cornified Envelope Formation: Difference Between Spontaneous Envelope Formation In Vivo and In Vitro. Journal of Investigative Dermatology;89(1):51-58. — DOI: 10.1111/1523-1747.ep12580383
7. Lützow-Holm C, Heyden A, Huitfeldt HS, Brandtzaeg P, Clausen OPF (1994). Differential effects of topical retinoic acid application on keratin K1 and filaggrin expression in mouse epidermis. Differentiation;57(3):179-185. — DOI: 10.1046/j.1432-0436.1994.5730179.x
8. Katugampola RP, Finlay AY (2005). Oral retinoid therapy for disorders of keratinization: single-centre retrospective 25 years' experience on 23 patients. British Journal of Dermatology;154(2):267-276. — DOI: 10.1111/j.1365-2133.2005.06906.x
9. Kundu S, Rai B, Shukla A (2021). Prevalence and determinants of Vitamin A deficiency among children in India: Findings from a national cross-sectional survey. Clinical Epidemiology and Global Health;11:100768. — DOI: 10.1016/j.cegh.2021.100768

PubMed Topic Searches

• PubMed — Phrynoderma and follicular hyperkeratosis
• PubMed — Vitamin A deficiency and skin keratinization
• PubMed — Retinoic acid and epidermal differentiation
• PubMed — Keratosis pilaris (the common look-alike)
• PubMed — Vitamin A deficiency, malabsorption, and serum retinol

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Connections

• Vitamin A Deficiency Hub
• Night Blindness & Eye Damage
• Weakened Immunity & Infections
• Poor Growth & Child Mortality
• Vitamin A Overview
• Vitamin A and Skin / Cellular Differentiation
• Vitamin A Food Sources
• Eczema
• Psoriasis
• Acne
• Vitamin E
• Vitamin C
• Zinc
• Omega-3 Fatty Acids
• Beef Liver
• Sweet Potatoes

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