The Science of the
Scalp Environment

Biotin is a coenzyme for the carboxylases, the enzymes of fatty acid and amino acid metabolism relevant to maintaining healthy skin and hair [1]. In a study of women complaining of hair loss, 38% showed biotin deficiency [1]. Without a proven deficiency the picture thins out: a systematic review found an underlying pathology in all 18 documented cases and no sufficient evidence for healthy individuals [2]. In a randomised crossover trial, oral biotin alone did not significantly increase the hair growth rate (p = 0.53); only the combination with minoxidil did [3] — though ten participants and fourteen days per arm is a narrow basis. And all three papers examine oral biotin. There is no comparable body of evidence for biotin applied to the scalp; that part remains a hypothesis.

Why it is in every serum regardless: because the deficiency is documented and not rare — 38% in the group cited [1]. Where biotin is missing, the carboxylases of fatty acid and amino acid metabolism stop working, and skin and hair are the tissues where that becomes visible [1]. Providing a water-soluble coenzyme whose absence has documented consequences is a decision with a clear benefit-risk profile. The study on topical use is missing. The reason it is in the formula is not.

Study type Observational study in humans · Review · Randomised controlled trial

References [1] Trüeb 2016 · [2] Patel 2017 · [3] Valentim 2024

Contained in PURE, SENSITIVE and MEN.

Niacin is the precursor of the coenzymes NAD and NADP, which transfer hydrogen in the energy metabolism of every cell [4]. For topically applied niacinamide, which the body can interconvert with niacin, a stabilised epidermal barrier function is documented in humans: lower transepidermal water loss, higher moisture content of the horny layer [4]. The effects on keratin synthesis and keratinocyte differentiation described in the same paper come from cell culture, not from humans. For hair there is exactly one controlled study: a placebo-controlled pilot trial in 60 women in which topical niacin derivatives significantly increased hair fullness after six months (p = 0.04) [5]. What was tested there were octyl and tetradecyl nicotinate — not niacin, and not this serum.

Why it is in the formula regardless: because the scalp is the target tissue, not the hair fibre. The barrier effect was measured in humans [4] — on exactly the tissue our serums meet. NAD and NADP are also the hydrogen carriers of every cellular respiration; formulating for a tissue with a high division rate without them would be the stranger decision. The hair side of the evidence is thinner than the skin side — and the skin side is what niacin stands for here.

Study type Review · Randomised controlled trial

References [4] Gehring 2004 · [5] Draelos 2005

Contained in PURE, SENSITIVE and MEN.

Pantothenic acid is a building block of coenzyme A, a central cofactor of cellular metabolism, and is essential to normal epithelial function [6]. The topical evidence exists for its alcohol analogue dexpanthenol: in double-blind, placebo-controlled trials it improved stratum corneum hydration and reduced transepidermal water loss [6]. The stimulation of fibroblast proliferation described there comes from cell culture and animal models. Two limitations remain. The substance studied is dexpanthenol while our declaration reads pantothenic acid, and what was studied was skin, not hair growth.

Why it is in every serum regardless: because coenzyme A is no niche molecule — it is a cofactor for reactions of carbohydrate, fatty acid and protein metabolism at the same time, and pantothenic acid is its building block [6]. It is essential to normal epithelial function; that is the starting point of the review we cite, not its open question [6]. Topical use of its analogue dexpanthenol is moreover considered well tolerated, with minimal risk of irritation or sensitisation [6]. What is missing is the study on hair — not the substance.

Study type Review

References [6] Ebner 2002

Contained in PURE, SENSITIVE and MEN.

Pyridoxal 5-phosphate is the active form of vitamin B6 and a cofactor in more than 140 enzymatic reactions, including central steps of amino acid metabolism [7]. Amino acids are the building blocks of keratin, the hair protein. That is where the evidence ends: no study examines vitamin B6 applied to the scalp. B6 stands here as a biochemically reasoned hypothesis.

Why it is in the formula regardless: because a missing study is not a missing mechanism. Pyridoxal 5-phosphate is a cofactor in more than 140 biochemical reactions in the cell, and most of them concern the synthesis and breakdown of amino acids [7] — the building blocks of keratin. That is why we use the active coenzyme form and not pyridoxine, which the body would first have to convert. Within the B-vitamin blend, B6 covers the amino acid step that biotin and pantothenic acid do not address. Of our ingredients, B6 is the least researched.

Study type Review

References [7] Parra 2018

Contained in PURE, SENSITIVE and MEN.

Ascorbic acid stimulates collagen synthesis and contributes to the skin's antioxidant defence [8]. For topical use, however, the same review notes that efficacy — unlike dietary intake — is poorly understood [8]. Oxidative stress is discussed as one mechanism contributing to the ageing of hair and hair follicles; the author himself calls that evidence circumstantial [9]. Whether topical vitamin C counteracts it has not been shown. We list it as an antioxidant, not as a promise.

Why it is in PURE and MEN regardless: because the cofactor role of ascorbic acid is not in dispute — it stabilises the tertiary structure of collagen via the proline and lysine hydroxylases [8], and the connective tissue around the follicle is part of the environment this page is about. We also declare ascorbic acid itself rather than a stabilised derivative: derivatives must first be converted back into ascorbic acid in the tissue, and whether that happens reliably is an open question [8]. What we do not claim is a benefit for hair. What we do is use the substance that is actually being researched.

Study type Review

References [8] Pullar 2017 · [9] Trüeb 2009

Contained in PURE and MEN. SENSITIVE does without it.

Silver ions act antibacterially: studies on cultures of E. coli and S. aureus show that silver disrupts bacterial DNA replication and protein function [10]. That is a bacterial culture in the laboratory — not humans, not the scalp. That a balanced scalp microbiome is linked to a healthy scalp has been described in humans: a comparative study of 140 women with and without dandruff [11]. The link between the two — silver in a serum improves the microbiome — we have not tested; it remains a hypothesis.

Why it is in SENSITIVE regardless: because the alternative would be worse for this product. SENSITIVE is formulated for sensitive scalps, and there alcohol is an irritant — it strips lipids and water and works against the barrier you are trying to stabilise. An aqueous serum still cannot do without antimicrobial protection. Silver ions cover that task, and their mechanism is described at the molecular level [10] — measured in bacterial culture, however. What follows from that is a formulation decision, not a microbiome promise.

Study type In-vitro study (bacterial culture) · Observational study in humans

References [10] Feng 2000 · [11] Saxena 2018

Only in SENSITIVE — where it replaces alcohol and conventional preservatives.