TESTING
77
Evaluating a serum for treating thinning hair
Nalini Kaul, Barrie Drewitt - Princeton Consumer Research
Hair thinning and hair loss (alopecia) is a prevalent concern, affecting both sexes, the world over. Although non-life-threatening, alopecia affects aesthetics, social activities, self-esteem and the quality of life.1-3
Alopecia is considered a common
symptom of several pathologies, involving inflammation, thyroid dysfunction or infection.4 Hair loss, is caused by an imbalance of the
hair growth cycle resulting from various factors, including ageing, metabolism, genetics, stress, nutritional, medical and environmental.5
These
factors lead to a reduced number of growing (anagen) hairs combined with an increased number of degenerating (telogen) hairs. Hair follows a repeated growth cycle with three phases: anagen lasting three to five years, catagen lasting about three weeks, and telogen lasting about four months, followed by shedding of hair.6 During telogen-resting phase, hair is shed and the next cycle is initiated.7-8
Ninety percent of the
hair on the healthy scalp is growing, while some are resting. Hair loss affects both sexes, albeit differently. In women, diffuse hair loss is seen and they
lose hair from the top of the head, while in men hair loss can be sizeable, affecting the top of the head and the temporal area. Approximately 50% of women have visible hair loss by the age of 60 years, while men tend to lose hair by the age of 50 years.9
The link between scalp health, hair growth and quality A healthy scalp breeds healthy hair. Ample evidence exists that establishes a link between scalp health, hair growth and quality.10
there is an increasing demand for products that support both scalp and hair health. A wide range of interventions including both
pharmaceuticals and cosmetics have been used to address hair loss. Drugs like 5-alpha reductase inhibitors finasteride and minoxidil are often employed for treatment, but they have shown various side effects.11,12
Need for new treatments It is therefore necessary to identify new, safe, and effective alternative treatments for hair thinning and hair loss. Interest in natural products - bioactive products promoting hair growth with less side effects and better safety is rising. A recent review provided a database of phytochemicals for hair-growth-promoting
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effects, along with their underlying mechanisms of action.13
Hair follicle cycling is tightly regulated by
molecular pathways such as Wnt/β-catenin, sonic hedgehog (Shh), and 5α-reductase activity. These pathways directly influence the
Therefore,
transition between the growth (anagen), regression (catagen), and resting (telogen) phases. Dysregulation of these signals contributes to shortened anagen, follicular miniaturization, and eventual alopecia. ■ Wnt/β-catenin pathway: Essential for activating dormant hair follicles and initiating new anagen growth. Natural compounds like caffeine have been shown to upregulate β-catenin signalling, thereby promoting hair shaft elongation.14 ■ Sonic hedgehog signalling: Critical for follicle morphogenesis and maintenance. Botanical extracts such as rosemary oil have demonstrated stimulatory effects on this pathway, leading to enhanced follicle density in animal models.15 ■ 5α -reductase inhibition: This enzyme converts testosterone to dihydrotestosterone (DHT), a major factor in androgenetic alopecia. Saw palmetto extract and pumpkin seed oil are natural 5α-reductase inhibitors, with clinical evidence showing improved hair counts and thickness in men with mild to moderate androgenetic alopecia.16,17 By targeting these molecular mechanisms,
phytochemicals provide a multi-pathway approach that may not only stimulate growth but also protect follicles from hormonal and oxidative stress–induced damage. This mechanistic diversity supports the
rationale for developing hair products that combine such natural actives, which have the potential to be more effective than minoxidil and finasteride.18
More hair products (serums, tonics,
growth promoters, conditioners, and cleansers) with natural ingredients are being developed for the treatment of hair thinning and loss.19,20 These include primarily oils, plant extracts,
botanical based dietary supplements, which promote both scalp health, hair growth and quality.21,22
With demand at an all-time high, and
new products constantly being introduced for hair and scalp health, testing for their efficacy, safety and product acceptability becomes very important. Clinical studies to test anti-hair loss or
hair-growth products are generally designed for three to six months or longer on volunteers with mild to moderate hair loss. Methodologies for evaluation include non-invasive techniques (hair counts, pull tests, pluck tests, standardized wash test, photographs, dermoscopy, hair weight, phototrichogram, trichoscan, electron microscopy and invasive techniques, such as a scalp biopsy.23,24
March 2026 PERSONAL CARE MAGAZINE
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