Hair Growth Serum: The Complete Guide

Last updated: March 2026 — Written by the ORVOVA team, reviewed by our dermocosmetics advisor.

You find hair on your pillow. In the shower, on your brush, between your fingers when you run your hand through your lengths. At first you do not pay attention. Then one morning, in front of the mirror, your parting looks wider, your temples thinner, and that vague impression hardens into a certainty: you are losing your hair.

For women, hair loss is still a taboo subject. It is rarely talked about, it carries a lot of guilt, and you end up alone facing an avalanche of contradictory information. Miracle supplements, £40 shampoos, hair oils with wildly overstated promises...

This article takes the opposite approach to the marketing. We are going to unpack what dermatological research actually knows about hair regrowth in women, identify the actives whose efficacy is documented, and give you a realistic protocol — no false promises, no artificial urgency.

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Why hair falls out: the 5 main causes in women

Before you go looking for a hair growth serum, you need to understand why the shedding is happening. The causes are often multiple and compound one another. Here are the five most common.

1. Telogen effluvium (cause number 1)

This is the most common form of hair loss in women. Intense stress — physical or emotional — pushes an abnormal proportion of follicles into the resting (telogen) phase. Two to three months later, those hairs fall out all at once. Childbirth, surgery, emotional shock, a restrictive diet, an infection: the triggers are many.

The good news: telogen effluvium is reversible. Once the stressor is resolved, the hair cycle picks up again. A suitable hair serum can speed that recovery up significantly.

2. Female pattern hair loss

Unlike men, women with androgenetic alopecia do not develop outright baldness but a diffuse thinning across the crown. The follicles gradually miniaturise under the effect of androgen hormones. It affects around 40% of women after 50, but can begin as early as 25.

In this case, acting early is decisive. The sooner you intervene, the more of their productive capacity the follicles keep.

3. Nutritional deficiencies

Iron, zinc, vitamin D, biotin, protein: hair is a tissue with very high metabolic activity. Even a moderate deficiency affects keratin synthesis. Women are particularly exposed because of menstruation (iron deficiency) and restrictive diets.

Tip: blood work (iron, ferritin, vitamin D, TSH) should be your first move when faced with persistent shedding. No serum will make up for a deep deficiency.

4. Hormonal imbalance

Coming off contraception, PCOS (polycystic ovary syndrome), perimenopause, thyroid disorders: hormonal fluctuations directly disrupt the hair growth cycle. The hair follicle has hormone receptors and reacts to every variation.

5. Mechanical and chemical damage

Tight hairstyles (traction), repeated bleaching, chemical straightening, excessive heat: these practices weaken the hair shaft and can damage the follicle permanently (traction alopecia). It is an often underestimated cause, yet an easy one to correct.

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The actives that work, according to science

The hair care market is full of ingredients with exotic names. But what does the scientific literature actually say? Here are four actives whose efficacy on female hair loss is backed by published clinical studies.

Redensyl: the alternative to Minoxidil

Developed by the Swiss laboratory Induchem, Redensyl is a patented complex combining DHQG (dihydroquercetin-glucoside) and EGCG2 (epigallocatechin gallate-glucoside). Its mechanism of action is unique: it reactivates the stem cells of the hair follicle (the ORSc cells) and reduces perifollicular inflammation.

The reference clinical study (2014, published by Induchem, double-blind, on 26 volunteers) showed:

• +17% of hairs in the anagen (growth) phase after 84 days
• -17% of hairs in the telogen (resting/shedding) phase
• An improved anagen/telogen ratio in 85% of subjects

Redensyl has the major advantage of not causing the rebound effect sometimes seen when Minoxidil is stopped. It is also suitable for sensitive scalps and requires no prescription.

Aminexil: the follicle's protector

Aminexil (diaminopyrimidine oxide) is a derivative of Minoxidil without its systemic side effects. Its action specifically targets perifollicular fibrosis: it stops the collagen around the root from hardening, preserving the suppleness of the tissue and the hair's anchorage.

Several clinical studies (notably Kligman, 2003) have demonstrated a 10 to 15% reduction in shedding after 6 weeks of regular use. Aminexil is particularly relevant in reactive hair loss where the hair's anchorage is weakened.

Rosemary essential oil: the substance behind the "natural"

Rosemary (Rosmarinus officinalis) is not just a trending ingredient on social media. A randomised study published in SKINmed (Panahi et al., 2015) compared rosemary essential oil with 2% Minoxidil over 6 months. The result: both groups achieved a comparable increase in hair count, with less scalp irritation in the rosemary group.

The mechanism? Rosemary stimulates local microcirculation, inhibits 5-alpha-reductase (the enzyme involved in androgenetic alopecia) and has anti-inflammatory and antioxidant properties.

Important: these results concern concentrated essential oil at a precise dose, not the diluted rosemary water you see on TikTok. Dosage and formulation matter enormously.

Anagain: restarting the cycle

Anagain is an organic pea extract (Pisum sativum) that acts on the cells of the follicle's dermal papilla. Its mechanism: it increases the expression of the signal molecule FGF7 (Fibroblast Growth Factor 7), which tells resting follicles to start a new growth cycle.

The clinical trials (Mibelle Biochemistry, 2012) report:

• A +78% increase in the ratio of growing hairs to shedding hairs after 3 months
• A faster transition from the telogen phase to the anagen phase

Anagain is particularly suited to women whose hair loss is linked to a shortened hair cycle (hair that grows for less time before falling out).

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To go further on this subject, read our guide to the dermaroller for hair regrowth.

How to choose a hair growth serum: criteria and traps to avoid

With so many products out there, how do you sort the wheat from the chaff? Here are the objective criteria to check before investing in a hair serum.

What to check

• The concentration of actives — A serum that lists an active without stating its percentage is probably hiding a homeopathic dose. The effective concentrations are documented: 2 to 3% for Redensyl, 1.5 to 2% for Aminexil, 2 to 3% for rosemary. Demand transparency.
• The application system — A serum has to reach the scalp, not sit on the lengths. Roll-on or targeted-pipette applicators are more effective than sprays that scatter.
• The synergy of actives — A single active, however well dosed, will always have less impact than a formula combining several complementary mechanisms of action (restarting the cycle + protecting the follicle + local stimulation).
• No occlusive silicones — Silicones (dimethicone, cyclomethicone) give a silky feel but form a film that can prevent actives from penetrating. A good scalp serum contains none.
• The clinical studies cited — A serious brand references the studies behind its actives. Be wary of "consumer tests" on 20 people: those are not scientific studies.

The red flags

• "Visible results in 7 days" — The hair cycle lasts 2 to 6 months. No topical product produces significant results in a week.
• "Guaranteed regrowth" — Regrowth depends on the state of the follicles, the cause of the shedding and individual factors. Nobody can guarantee it.
• Formulas with 30+ ingredients and no stated doses — The longer the list, the more likely each active is underdosed.
• No scientific references at all — If a product cites no study, no patent and no dosage, that is a clear signal.

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The 90-day protocol: what to expect week by week

A hair growth serum is not an instant product. The hair follicle has its own biological rhythm, and you have to respect that tempo. Here is a realistic timeline based on what the science and real-world feedback tell us.

Weeks 1 to 2: settling into the routine

No visible change, and that is normal. The goal is to build the habit of applying the serum daily, ideally in the evening, on a dry or slightly damp scalp. The roll-on makes it easy: parting by parting, massaging gently with your fingertips for 1 to 2 minutes to help it penetrate.

What you may feel: a slight cooling sensation from the rosemary. There should be no excessive tingling — if there is, space out the applications.

Weeks 3 to 4: the stabilisation phase

This is often the most discouraging phase. You may notice a slight increase in shedding. Do not panic: it is a sign that the hair cycle is resynchronising. Hairs in the late telogen phase are being "pushed out" by the new hairs starting their growth. This phenomenon, called shedding, generally lasts 1 to 2 weeks.

A positive indicator: if you notice short little hairs (1-2 cm) along your hairline, regrowth has begun. They are fine and light — that is normal.

Weeks 5 to 8: the first signs

Daily shedding starts to decrease noticeably. If you count the hairs on your brush (a common reflex), you should see a gradual drop. The scalp may feel healthier, less oily or less dry depending on your profile.

This is the point where many women stop their treatment, thinking "it is not working fast enough". A mistake: the follicles are resuming their activity, but the hair has not yet reached a visible length.

Weeks 9 to 12: tangible results

This is the payoff phase. Studies on Redensyl and Anagain place measurable results (trichoscopy, hair counts) at around 84 days — exactly 12 weeks. At this stage:

• Hair density increases, especially in the most affected areas (parting, temples, crown)
• Existing hairs are thicker (improved shaft diameter)
• New growth measures 2 to 4 cm and starts blending into the rest of the hair
• Daily shedding settles within the physiological norm (50 to 80 hairs a day)

Important note: results vary with the initial cause of the shedding, how long the problem has been going on and individual factors (genetics, diet, stress). Recent telogen effluvium will respond faster than androgenetic alopecia that has been established for years.

Beyond 90 days: the maintenance phase

After 3 months, you have two options: keep applying daily to continue optimising results, or move to a maintenance rhythm (3 to 4 applications a week). The transition should be gradual.

Unlike Minoxidil, actives such as Redensyl and Anagain do not cause an abrupt rebound effect when you stop. That said, if the underlying cause persists (hormones, genetics), regular maintenance is still recommended.

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You may also like our article on Redensyl for hair.

Frequently asked questions

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Conclusion

Hair loss in women is neither inevitable nor "all in your head". It is a biological signal that deserves an informed, methodical response.

Remember three principles:

1. Identify the cause — Blood work and, if necessary, a dermatology consultation are the essential starting point.
2. Choose documented actives — Redensyl, Aminexil, Anagain and rosemary all have published clinical studies behind them. Favour formulas that state their concentrations.
3. Give yourself time — 90 days minimum, with regular application. The hair cycle is not negotiable.

If you are looking for a formula that brings these four actives together at clinical doses in a format that works day to day, we designed the ORVOVA Roll-On Hair Growth Serum with exactly that in mind: transparent about its concentrations, effective on the scalp, with no overblown promises.

Your hair follows its own calendar. Respect it, support it with the right tools, and the results will follow.