The Science Behind Hair & Scalp Rejuvenation: How to Revive Thinning H

Thinning hair is a normal part of aging for men and women alike — but understanding exactly why it happens opens the door to targeted, science-backed solutions. From aging hair follicles and hormonal shifts to chronic inflammation and reduced blood flow, multiple processes are at work, and addressing them requires a multi-pronged approach.

In This Guide

01Targeting Hair Follicles for Thicker, Fuller Hair
02Why Hair Thins as You Age
03How to Treat Hair Thinning and Hair Loss
04Picking the Right Shampoo and Conditioner

THE BASICS

From Thinning to Thicker and Fuller Hair: Targeting Hair Follicles

Your genes determine the color of your hair, whether it is straight, helical or wavy, and its length, diameter and density. As we age however, everyone's hair starts to turn grey and thin or even bald. This is due to changes happening inside the scalp where the hair follicles reside.

At any given time, the hair follicle is in one of three stages that either represents a growth phase (anagen), or a period of non-growth (catagen, telogen). Catagen is a period of regression and telogen a period of rest. Anagen typically lasts 2–8 years with a hair growth rate of approximately 1 cm per month. Catagen lasts for several weeks and telogen lasts for 2–4 months.

Hair follicle growth stages: anagen, catagen, and telogen — Growth stages reproduced from Jang et al. 2023

There is a lot going on within the hair follicle. It contains several specialized types of cells. Hair Follicle Stem Cells (HFSCs) are responsible for regenerating the hair follicle for the anagen growth phase. Matrix cells give rise to the actual hair shaft itself. Dermal papilla cells (DPCs) regulate the growth of matrix cells by sending out growth factors and extracellular matrix factors that determine the growth stage. Melanocytes are cells that make the melanin pigments which give hair its color.

There are also nerve fibers and capillaries that provide blood. The sebaceous gland secretes oily sebum which is what makes your hair and scalp oily. On the skin side of the hair follicle there is also a connective tissue layer which consists of two layers of collagen fibers (Natarelli et al. 2023).

KEY INSIGHT

The only living, growing part of your hair is underneath your scalp skin where the hair follicle resides. To increase hair growth, thickness and density, a scalp serum targeting the follicle is essential — not just products applied to the visible hair strand.

Full Follicle Serum

A scalp serum with 14 actives — including peptides, growth factors, caffeine, vitamins, and botanicals — designed to target the multiple root causes of thinning hair.

Shop Full Follicle

THE SCIENCE

Why Hair Thins as You Age

As you age, there is an increase of hair follicles in telogen versus anagen. The length of the anagen growth stage also decreases. Hair sheds prematurely with aging. Some hair follicles disappear altogether. Loss of melanocytes in the hair bulb leads to a loss of hair color (Buffoli et al. 2014, Natarelli et al. 2023).

Androgenic Alopecia (DHT)

One major cause is androgens, which leads to androgenic alopecia — more commonly known as male pattern baldness. This is very common and affects nearly 50% of men by age 50. A potent androgen called dihydrotestosterone (DHT) is largely responsible. DHT directly affects DPCs to signal a shortened anagen and a prolonged telogen, enhances death of hair cells, and causes follicular miniaturization (Bassino et al. 2020). With male pattern baldness, there is a genetically determined increased production of DHT in the frontal scalp. Women are also commonly affected, though typically with diffuse apical hair loss and a milder presentation (Villani et al. 2022).

Estrogen Loss (Perimenopause, Menopause, Postpartum)

In contrast to androgens, estrogen promotes lush hair growth — which is why hair often looks fuller during pregnancy. Postpartum, estrogen levels drop and that hair sheds. After menopause, estradiol drops to near zero, leading to thinning hair. Estrogen is also important for the integrity of the skin around hair follicles, so post-menopausal loss of collagen, elastin, GAGs, and dermal vascularization may compound the thinning (Villani et al. 2022).

Cellular Senescence

All cells in your body undergo "senescence" as you age — a gradual deterioration in a cell's ability to function, divide, and grow. There is a general decline in HFSC activity and a drop in growth factor production that decreases the hair follicle's regenerative capacity. Senescent cells also show decreased mitochondrial efficiency, leading to greater production of damaging free radicals (Deng et al. 2022).

Chronic Inflammation

Aging is associated with chronically elevated levels of inflammatory cytokines which inhibit HFSC function and can impair melanocytes, contributing to graying. Obesity, psychological stress, and the stress hormone corticosterone all drive chronic inflammation around the hair follicle. Demodex mite infestation also increases with aging, contributing further to follicular inflammation (Liang et al. 2023). Animal studies show that reversing inflammation can lead to some hair regrowth in aged mice (Jang et al. 2023).

Oxidative Stress

The aging body's ability to clear reactive oxygen species (ROS) declines. Studies show a buildup of hydrogen peroxide in white hair shafts at millimolar concentrations, leading to a loss of melanocytes and pigment. Environmental drivers of oxidative stress include UV rays, pollution, smoking, nutritional deficiency, and inflammation. Genetic factors also heavily influence onset — Asian and African people have later onset and less grey hair than Caucasians. Unless caused by rare nutritional deficiencies, grey hair has no reliable treatment (Kumar et al. 2018, Villani et al. 2022).

Reduced Blood Flow

Dermal microcirculation is essential for hair maintenance — delivering growth factors, nutrients, and bioactive molecules while removing waste products. Vascular endothelial growth factor (VEGF), which regulates angiogenesis and hair follicle size, decreases with age. Blood flow to the dermis also decreases with age, and factors like cigarette smoking cause further changes in the microvasculature of the dermal hair papilla (Bassino et al. 2020, Trueb 2009).

ECM (Extracellular Matrix) Degradation

Hair follicle and skin aging is associated with a loss of ECM integrity. Structural proteins like collagen and elastin decline, reducing anchoring of hair in the follicle and increasing shedding. Elevated stiffness in the basement membrane deactivates HFSCs. Photoaging leads to elastosis — where degraded elastin accumulates — which can precede hair thinning. Bald scalp regions often show signs of solar elastosis (Jang et al. 2023, Trueb 2009).

Other Causes

Additional causes include autoimmune disorders such as Alopecia Areata, Frontal Fibrosing Alopecia (sometimes found in postmenopausal females), drug-induced telogen effluvium, thyroid disorders, and dietary deficiencies in vitamins and essential amino acids (histidine, leucine, valine) as well as non-essential amino acids (alanine, cysteine). Chemotherapy can also lead to hair loss; scalp cooling is a technique used to mitigate this (Natarelli et al. 2023, Villani et al. 2022).

TREATMENT

How to Treat Hair Thinning and Hair Loss

Prescription Medications

For androgenic alopecia, topical minoxidil (for men and women) and oral finasteride/Propecia (for men only) are the only FDA-approved prescription medications. Minoxidil increases blood flow and is anti-inflammatory and anti-androgen, though it can cause contact dermatitis in some users (Ohn et al. 2019, Natarelli et al. 2023).

Topical Minoxidil

About 60% of men with male pattern baldness respond to topical minoxidil. Approved for men and women. Can cause contact dermatitis. Continuous use is required — hair regrowth reverses when treatment stops.

Oral Finasteride

99% of men with male pattern baldness respond positively. Inhibits 5-alpha reductase (the enzyme that converts testosterone to DHT). For men only. Side effects include sexual dysfunction, depression, and increased risk of prostate cancer. Continuous use required.

Dutasteride

Another 5-alpha reductase inhibitor, prescribed off-label for hair loss (Villani et al. 2022, Liang et al. 2023).

Red Light Therapy

Also known as photobiomodulation therapy (PBMT) or low-level laser therapy (LLLT). FDA-approved for hair loss. Does not require a prescription; several devices have shown clinical efficacy.

Hair Transplantation

Can treat bald areas effectively, but transplanted follicles remain subject to the same aged skin environment and hormonal factors that caused initial hair loss (Jang et al. 2023).

Topical Actives Available Over the Counter

Many topicals are not FDA approved but have shown efficacy in studies. These include anti-fungals such as ketoconazole (a cortisol inhibitor that can help increase hair density) and prostaglandins such as bimatoprost and latanoprost (popular in eyelash growth serums) (Natarelli et al. 2023).

Below, we go over the evidence supporting modern topicals that use actives such as peptides, growth factors, caffeine, vitamins, and botanicals — all of which have been shown in studies to achieve clinical results. Where relevant, we detail the actives found in our Full Follicle line.

Peptides

Acetyl tetrapeptide-3 — one of the 14 actives in our Full Follicle line — stimulates DPCs to increase ECM components that improve hair anchoring and reduce shedding. This elongates the anagen growth phase and has been shown to stimulate hair growth.

In a clinical study of 32 patients with mild to moderate androgenic alopecia, acetyl tetrapeptide-3 with ginseng extract and biochanin A demonstrated comparable efficacy at 24 weeks to 3% minoxidil in increasing terminal hair counts (Lueangaran and Panchaprateep 2020).

In an industry-sponsored clinical study, acetyl tetrapeptide-3 with red clover extract boosted the percent of hair follicles in anagen by 15% and decreased follicles in telogen by 52% compared to placebo after 4 months of daily application. Benefits were also found in rinse-off form (shampoo and conditioner) (Capixyl).

Growth Factors and Platelet Rich Plasma

The Full Follicle line uses a growth factor complex of five growth factors (EGF, aFGF, IGF-1, VEGF, bFGF) derived from vegan lab-derived sources. A diverse array of growth factors regulate the stages of hair growth. Epidermal growth factor (EGF) turns on hair follicle growth to mark the beginning of anagen. IGF-1 deficiency is implicated in androgenic alopecia. VEGF stimulates proliferation of DPCs during anagen (Ohn et al. 2019).

Due to synergies between growth factors, a combination rather than a singular one is more effective (Krane et al. 1991). Platelet rich plasma (PRP) is a popular route for delivering growth factors to follicles, with clinical studies showing increased hair density and diameter in men, and hair diameter in women (Paichitrojjana and Paichitrojjana 2022, Natarelli et al. 2023). However, the expense of PRP and its human source makes synthetic growth factors more popular.

Clinical and corresponding in-vivo and ex-vivo studies demonstrate that a mix of synthetic IGF-1, aFGF, bFGF, VEGF and EGF increased cell proliferation in DPCs, along with greater elongation of the hair shaft (Bio-placenta). Synthetic growth factors have also been shown to promote hair growth in animal models (Choi et al. 2018).

Caffeine

Caffeine counteracts DHT-induced miniaturization of the hair follicles and is included in our Full Follicle line. In one in-vitro study using scalp hair follicle biopsies from male subjects, testosterone suppressed hair growth while caffeine stimulated it — and caffeine counteracted the effects of testosterone on the hair follicle (Fischer et al. 2007).

Clinical studies show caffeine can penetrate into hair follicles after topical application and was found to be more effective than 5% minoxidil in men with androgenic alopecia. In women, a shampoo with caffeine significantly reduced hair loss (Bansal et al. 2012, Bassino et al. 2020).

Vitamins (B5 and B7)

The Full Follicle line contains panthenol (Vitamin B5) and biotin (Vitamin B7). Biotin deficiency has been associated with hair loss; while dietary deficiency is extremely rare in the US, it can occur in up to 50% of pregnant women (Almohanna et al. 2019).

Panthenol (B5) deficiency is not directly associated with hair loss, but studies show meaningful benefits to scalp and follicle health. One study showed panthenol helped DPC survival, reduced markers for apoptosis and senescence in aged follicles, triggered and elongated the anagen phase, and increased VEGF expression (Shin et al. 2021). Panthenol also coats and penetrates the hair shaft, where it strengthens hair from within.

Botanicals and Phytocompounds

Botanical plant extracts and phytocompounds have anti-inflammatory and antioxidant activity, but also reduce hair fallout and stimulate growth through additional mechanisms (Deng et al. 2022). The Full Follicle line contains Swiss Apple Stem Cells, Red Clover, Rosemary, Ginseng, Eucalyptus, Green Tea, and Grapeseed.

Swiss Apple Stem Cells: Certain apple species contain procyanidins that improve hair density, weight, and keratin content (Bassino et al. 2020). Procyanidin B-2 has been clinically shown to improve hair density in androgenic alopecia compared to placebo. These procyanidins are harvested via plant stem cells from Malus Domestica. Daily application of a topical stem cell extract reduced hair shedding by 34% after one month and by 41% after two months, with visible improvement in density (PhytoCellTech).

Red Clover: Contains biochanin A, a phytoestrogen which inhibits 5-alpha-reductase activity (Skulj et al. 2019). Synergistic with acetyl tetrapeptide-3; in combination, found to increase hair thickness and density (Capixyl).

Rosemary: Thought to increase hair growth by stimulating microcapillary perfusion. Studies show improved blood circulation and vascularity induced by rosemary helps hair follicle regeneration similarly to minoxidil. Clinical studies show comparable efficacy between rosemary and minoxidil (Natarelli et al. 2023).

Ginseng (Panax Ginseng): Contains saponins, polysaccharides, and phenolic compounds with anti-inflammatory and antioxidant activity. Believed to improve blood flow, induce anagen, and have anti-apoptotic effects on outer root sheath keratinocytes. Topical ginseng plus minoxidil was found more effective than minoxidil alone (Bassino et al. 2020).

Eucalyptus: Can improve blood circulation (Mamada et al. 2008).

Green Tea (Camellia sinensis): Contains EGCG, a polyphenol which stimulates human hair growth via proliferative and antiapoptotic effects on follicular dermal papillae cells (Bassino et al. 2020).

Grapeseed (Vitis Vinifera): Contains proanthocyanins with promising results for hair growth. Animal studies show grape-seed derived proanthocyanins can increase the transition from telogen to anagen and at 3% levels promoted hair growth comparable to 1% minoxidil (Takahashi et al. 1998).

HOW TO USE

Picking the Right Shampoo and Conditioner

Though hair growth and density rely on living hair follicles in the scalp skin, a beautiful head of hair also requires maintenance of the visible hair strands. Hair is naturally coated with a waterproof hydrophobic lipid layer made of 18-methyleicosanoic acid (18-MEA) that is bonded firmly to the fiber — it's not like oil floating on the surface that washes off easily (Gubitosa et al. 2019).

However, harsh cleansers as well as styling, coloring, perming, blow-drying, and high-friction combing will slowly remove this waterproofing coating and damage the interior parts of hair, leaving it brittle. This is particularly true for chemically treated hair. You want cleansing products that are relatively mild, plus a conditioner that can restore hair waterproofing and reverse damage while reducing friction during brushing and combing.

IMPORTANT

Not washing is not an option — it will lead to hair loss. The scalp is a dark, moist, sebum-rich environment ideal for microbes like Malassezia yeast. Without cleansing, Malassezia overgrowth contributes to dandruff, seborrheic dermatitis, and folliculitis (inflamed, infected hair follicles). Studies show frequent cleansing is necessary for scalp health and hair growth (Punyani et al. 2021).

Choosing a Mild, Effective Shampoo

Look for shampoos formulated for damaged and color-treated hair that contain milder detergents. Sulfates like SLS and SLES are popular but harsh, and carry a reputation for irritancy — it is a good idea to opt for sulfate-free products (Draelos 2010, D'Souza and Rathi 2015, Cline et al. 2018).

Those with thinning hair may also want a hair thickening shampoo that contains additional actives such as caffeine or botanicals that can help stimulate hair growth (Draelos 2010, D'Souza and Rathi 2015).

PRO TIP

The amount of oily sebum secreted by each person's scalp differs. Some people need to wash more, and some less — but overall, using an effective yet mild sulfate-free shampoo is the right approach for all hair types dealing with thinning.

What Conditioners Actually Do

No matter how mild the shampoo, washing hair makes it rough — that's where conditioners come in. Anionic surfactants leave a negative charge on the hair shaft; conditioners neutralize this with cationic molecules. Damaged hair also carries a negative charge from its exposed inner layers. Neutralizing this charge diminishes static, frizz, and friction during brushing.

Panthenol (Provitamin B5) is popular in conditioners as it can stick to hair and absorb into the deeper layers where it acts as a humectant, holding onto water to keep hair hydrated. Plant oils and butters contain fatty acids that can penetrate and coat the hair shaft, improving its waterproofing. Conditioners restore the cuticle's waterproofing and the combability of hair using a combination of polymers, oils, and butters/waxes (Draelos 2010).

Mild Sulfate-Free Shampoo + Actives-Rich Conditioner + Scalp Serum

= Complete Hair Rejuvenation

Cleanse, condition, and treat at every step of your routine

For a more in-depth look at hair thinning science, refer to our Deep Guide, and for a simpler TLDR version check out our Concise Guide. You can also explore the full Full Follicle line here.

Full Follicle Serum

14 clinically studied actives — peptides, growth factors, caffeine, vitamins, and botanicals — working together to target the root causes of hair thinning at the scalp level.

Shop Full Follicle Serum

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