The scalp: the living part of the hair system

The scalp: the living part of the hair system

Count the sebaceous glands in a square centimetre of scalp and you land somewhere between 400 and 900. In the palm of the hand there are none at all. That one difference explains most of how the scalp behaves, and almost none of it is visible in a mirror.

Hair care in Sweden is overwhelmingly a conversation about the hair shaft: how it looks, how it breaks, what you put on it. The shaft is dead keratin. It has no blood supply, no metabolism and no capacity to repair itself. The living part of the system is the skin the shaft grows out of, and the follicle buried inside that skin. This article is about that part. We have written separately about the biology of the hair fibre, so here we stay below the surface.

The short version

• The hair shaft is dead keratin. The living part of the system is the scalp: skin carrying 400 to 900 sebaceous glands per square centimetre, a microbial community of its own, and follicles among the most metabolically expensive tissues in the body.

• The nuance that matters most: dandruff is not about how much sebum you make or how much yeast you carry, but about how susceptible your own skin is, and there is no test for that susceptibility. What has trial data behind it is an antifungal shampoo containing ketoconazole or ciclopirox, not anything you swallow.

• Hair Beautification provides Keranat millet seed extract at 300 mg per daily dose, the dose used in the ingredient's own studies, alongside 50 µg biotin, zinc and vitamin B6. Biotin and zinc contribute to the maintenance of normal hair. It is a food supplement, not a scalp treatment.

Health Royals Hair Beautification, hair supplement with Keranat millet extract, biotin and zinc

Hair from within at Health Royals

Hair Beautification is built around Keranat millet seed extract at 300 mg per daily dose, the dose used in the ingredient's own studies, with 50 µg biotin, zinc and vitamin B6. Biotin and zinc contribute to the maintenance of normal hair, zinc contributes to normal protein synthesis and vitamin B6 contributes to normal cysteine synthesis. It is a food supplement and not a scalp treatment, which is true of everything else you can swallow as well.

See Hair Beautification

What makes the scalp different from the skin on the rest of the body?

Density, mostly. The scalp carries more sebaceous glands, more hair follicles and more microbial life per square centimetre than almost any other site on the body.

The gland and the follicle are not separate structures. Together they form the pilosebaceous unit: the gland empties through a duct into the follicle, and its secretion travels up the follicular canal to reach the surface. A 2025 review in Cells puts sebaceous gland density on the scalp and forehead at 400 to 900 glands per square centimetre, with the palms and soles carrying none at all.

What those glands make is not simply oil. Sebum is a mixture of triglycerides, wax esters, squalene, cholesterol and free fatty acids, and two of those, squalene and wax esters, are produced nowhere else in human tissue.

The result is a very specific environment: lipid rich, relatively humid, mildly acidic, and perforated by tens of thousands of follicular openings. A 2026 review in Molecules calls this a specialised ecological niche that shapes a scalp microbial community distinct from skin elsewhere, carrying roughly 10,000 to 100,000 bacterial cells per square centimetre alongside a fungal population dominated by two species of Malassezia.

Why can a scalp be dry and flaking while the hair still goes greasy?

Because oiliness and barrier function are two separate things, and a scalp can have plenty of the first while failing at the second.

Dryness on the scalp is usually not a shortage of sebum. It is a stratum corneum losing water faster than it should and shedding in visible clumps rather than in invisible single cells. In seborrhoeic dermatitis, a 2025 narrative review in Biomedicines reports altered keratin expression and reduced ceramides and sphingolipids in affected skin. That is a barrier problem, not a moisture problem, and no amount of conditioner reaches it.

The Molecules review traces the same cascade at molecular level. Irritant lipid breakdown products activate inflammatory signalling, keratins K6, K16 and K17 are overexpressed, filaggrin is downregulated, and the barrier degrades further, which makes the next round easier. The authors describe the loop as self-perpetuating.

So a scalp can feel tight and flake in a Swedish February while the roots look oily by day two. The two observations are not in conflict, and treating the second usually makes the first worse.

What is dandruff, and is it the same thing as seborrhoeic dermatitis?

Dandruff is the mildest end of seborrhoeic dermatitis rather than a separate condition. The two sit on one spectrum, which is why the same treatments work across it.

StatPearls describes dandruff explicitly as the mildest form of seborrhoeic dermatitis and as its non-inflammatory variant. The prevalence figures follow the same logic. A 2025 review in the Journal of Cutaneous Medicine and Surgery puts dandruff at 17 to 50 per cent of adults and seborrhoeic dermatitis at 1 to 14.3 per cent, while the Biomedicines review gives a pooled global figure of 4.38 per cent. Roughly one person in two flakes. Roughly one in twenty has the inflammatory version.

The mechanism is a three-way interaction, and only one of the three is a microbe. Malassezia yeasts, chiefly M. restricta and M. globosa, live on almost every adult scalp. Their genomes are unusual: whole-genome analysis published in the Journal of Investigative Dermatology Symposium Proceedings found that M. globosa lacks a fatty acid synthase and carries 13 secreted lipases, so it cannot build its own fatty acids and must take them from host sebum. Splitting sebum triglycerides releases free fatty acids, among them oleic acid, which the Biomedicines review describes as penetrating the stratum corneum, promoting inflammation and inducing desquamation.

The third factor is the one that gets forgotten. StatPearls states plainly that neither the level of sebum produced nor the amount of yeast appears to be a significant factor in who develops the condition. Almost everyone carries the yeast. Not everyone reacts to it, and individual susceptibility is doing work we cannot yet measure.

Treatment is topical and reasonably well studied. A Cochrane review of 51 trials and 9,052 participants found ketoconazole gave a 31 per cent lower risk of failed clearance against placebo at four weeks, on low-quality evidence, and ciclopirox a risk ratio of 0.79 on moderate-quality evidence.

What does itching, or a scalp that hurts to touch, actually mean?

It means something is irritating or sensitising the skin, and unlike flaking it is not a symptom to interpret at home.

Sensitive scalp is common. A 2023 review in Skin Appendage Disorders puts it at 30 to 50 per cent of the general population, more often in women. Trichodynia, meaning actual pain in the scalp or in the hair itself, is reported by 17 to 35.7 per cent of people who are losing hair, again mostly women.

The proposed mechanisms are nerve hyperreactivity through TRPV1 channels, local immune activation, and the same barrier dysfunction described above with raised pH and increased water loss. The same review also lists what has to be ruled out first: seborrhoeic dermatitis, psoriasis, atopic dermatitis, contact eczema, postherpetic neuralgia. Those are diagnoses, not shampoo decisions.

1177 gives the practical version. Contact a health centre if seborrhoeic eczema is causing you significant trouble, and contact one as well if hair is coming out alongside itching or redness at the root, or if it has not regrown within six months. Persistent scaling, persistent itch, pain, or loss in defined patches belongs with a doctor. It does not belong with a supplement.

Does scalp massage do anything?

Possibly a little, but the evidence is thin enough that anyone calling it proven has not read it.

There are essentially two studies. The first, published in Eplasty in 2016, followed nine healthy Japanese men aged 25 to 46 who used a scalp massage device for four minutes a day for 24 weeks, with the untreated side of their own scalp as the comparison. Hair thickness went from 0.085 mm to 0.092 mm. Hair count on the massaged side fell significantly at 12 weeks before recovering, which the authors attribute to temporary telogen shedding.

The second is a survey. English and Barazesh contacted 1,899 people who had accessed online scalp massage instructions; 340 completed the questionnaire and 327 attempted the protocol, which was twenty minutes twice a day. Of those, 68.9 per cent reported that shedding had stabilised or that hair had regrown. The authors themselves list the problems: no control group, self-reported outcomes, choice-supportive bias, recall bias for both adherence and results.

Nine men with a device, and a self-selected survey with nothing to compare against. That is the whole evidence base. Massage is pleasant, costs nothing and is very unlikely to harm you. It is not a treatment, and it has never been tested as one.

What does the follicle need from the inside, and do B vitamins affect hair growth?

The follicle needs an unusual amount of energy, and among the B vitamins only biotin carries an authorised EU claim relating to hair.

Start with the metabolic bill. A growing follicle sustains one of the highest rates of cell division seen in any mammalian tissue, according to a 2021 paper in Scientific Reports, and meets that demand largely through aerobic glycolysis, converting about 90 per cent of its glucose to lactate even when oxygen is available. The same group showed that human scalp follicles run an internal Cori cycle, recycling their own lactate back into glycogen rather than exporting it.

That expense is the key to everything that follows. A tissue this costly is a tissue the body can afford to pause, because hair carries no survival function. Under illness, energy restriction or sustained physiological stress, hair is among the first things deprioritised.

On the nutrient side, the permitted claims list under Regulation (EU) 432/2012 authorises exactly three wordings about hair: biotin contributes to the maintenance of normal hair, zinc contributes to the maintenance of normal hair, and selenium contributes to the maintenance of normal hair. Vitamin B6 has authorised claims for normal protein and glycogen metabolism, for the reduction of tiredness and fatigue and for the regulation of hormonal activity, but none relating to hair. Botanical claims, including those for millet extracts, remain on hold in the EU register and have never been assessed to a conclusion. We say so because it is true, not because it helps.

Maintenance is the right word and it is a modest one. A 2017 review in Skin Appendage Disorders found 18 reported cases of biotin improving hair or nails, and in every one the patient had an underlying pathology. Biotin deficiency is uncommon. A 2019 review in Dermatology and Therapy concluded that biotin supplementation is not supported by the literature for androgenetic alopecia or telogen effluvium, and warned that high-dose biotin can produce dangerously false laboratory results. We have written more about biotin and what it does separately.

Why does hair fall out two to three months after the event that caused it?

Because the follicle does not release the hair when it stops growing it. It releases it at the end of a resting phase that lasts roughly four months.

In a healthy scalp about 85 per cent of follicles are in anagen, the growth phase, and 15 per cent in telogen, the resting phase. A follicle grows hair for close to four years, then rests for about four months before letting go.

Telogen effluvium is what happens when a trigger pushes an abnormal share of follicles into telogen at the same time. StatPearls describes a causative event approximately three months before the shedding starts, with a range of one to six months, and notes that under significant stress up to 70 per cent of anagen hairs can precipitate into telogen. The listed triggers are recognisable: acute febrile illness, severe infection, major surgery, childbirth, hypothyroidism, crash dieting, low protein intake, iron deficiency.

The delay is exactly why the cause gets missed. By the time the shedding is obvious in the shower drain, the influenza, the operation or the diet is two or three months in the past and no longer feels connected to anything.

For women this overlaps with a second, slower pattern. 1177 notes that people normally shed between 50 and 150 hairs a day, and that hereditary hair loss in women most often appears around menopause, thinning gradually until the scalp starts to show through. Those are two different processes on two different timescales, and only one of them reverses on its own. We have written about the biology of menopause elsewhere.

What does the evidence not show?

A great deal, and most of it is sold anyway.

It does not show that oily scalps cause dandruff. StatPearls is explicit that sebum quantity is not a significant factor, and near-universal Malassezia colonisation means yeast load is not either. Susceptibility carries the difference, and there is no test for it.

It does not show that scalp massage grows hair, for the reasons above. Nine unblinded men is a pilot, not a finding.

It does not show that vitamins or minerals improve hair in people who are not deficient. The 2019 Dermatology and Therapy review found insufficient data to recommend zinc supplementation even where deficiency exists, and framed micronutrient deficiency as a modifiable risk factor, which is a statement about deficiency and not about supplementation in general. It also notes the reverse: excess selenium and excess vitamin A are both associated with hair loss, so more is not a direction.

And it does not show, because no such evidence exists, that anything swallowed treats a scalp condition. Under EU food law nothing eaten may be presented as preventing, treating or curing a disease, and that rule exists for good reason here. Seborrhoeic dermatitis is a diagnosis with topical treatments that have trial data behind them. A capsule is not one of them, and this includes ours.

What is actually worth doing?

Wash often enough that sebum and its breakdown products are not sitting on the skin for days at a time. Frequency is individual, and the honest answer is that no trial can tell you your number.

If you flake, an antifungal shampoo containing ketoconazole or ciclopirox is the intervention with evidence behind it, and it is sold without prescription in Sweden. Use it on the schedule on the box rather than occasionally.

If scaling, itch or soreness persists, if hair comes out in defined patches, or if shedding continues past six months, book an appointment. That is a dermatological question with dermatological answers.

Eat enough. This sounds trivial and is not. Energy restriction, low protein intake and iron deficiency all appear on the trigger list for telogen effluvium, and all three are common in exactly the group that worries most about thinning hair.

And keep the categories apart. Hair Beautification is a food supplement built around Keranat millet seed extract at 300 mg, the dose used in its own studies, with biotin, vitamin B6 and zinc at reference intake levels as set out in the Nordic Nutrition Recommendations 2023. Biotin and zinc carry the authorised claim that they contribute to the maintenance of normal hair. It is not a scalp treatment, and neither is anything else you can swallow. More on how the hair system fits together sits on our hair page.

Further reading

Frequently asked questions

Why does my scalp itch?
Itch means something is irritating or sensitising the skin, and unlike flaking it is not a symptom to interpret at home. Sensitive scalp is reported in 30 to 50 per cent of the general population, more often in women. What has to be ruled out first is seborrhoeic dermatitis, psoriasis, atopic dermatitis and contact eczema, which are diagnoses rather than shampoo decisions.

Is dandruff the same thing as seborrhoeic dermatitis?
They sit on one spectrum. Dandruff is described as the mildest, non-inflammatory form of seborrhoeic dermatitis, which is why the same treatments work across the range. Roughly one adult in two flakes, while 1 to 14.3 per cent have the inflammatory version.

What actually helps against dandruff?
An antifungal shampoo containing ketoconazole or ciclopirox is the intervention with evidence behind it, and both are sold without prescription in Sweden. A Cochrane review of 51 trials and 9052 participants found a 31 per cent lower risk of failed clearance with ketoconazole against placebo at four weeks. Use it on the schedule on the box rather than occasionally.

Can a supplement do anything for a dry or flaking scalp?
No, and that applies to our own product as much as to anyone else's. Seborrhoeic dermatitis is a diagnosis with topical treatments that have trial data behind them, and under EU food law nothing eaten may be presented as preventing, treating or curing a disease. Hair Beautification is a food supplement, not a scalp treatment.

Does scalp massage work?
The evidence is two studies: nine Japanese men using a massage device for 24 weeks, and an uncontrolled survey in which 327 people had attempted a twenty minute routine. That is not enough to call massage a treatment. It is pleasant, costs nothing and is very unlikely to harm you, which is a smaller and more honest argument.

Why does hair fall out months after I was ill?
The follicle does not release the hair when it stops growing it. It releases it at the end of a resting phase lasting roughly four months. Telogen effluvium is therefore described with a causative event approximately three months before the shedding starts, with a range of one to six months. By the time it is obvious in the shower drain, the influenza, the operation or the diet no longer feels connected to anything.

Sources