FAQ
Questions, answered
Short answers first. Where an answer rests on research, the study is linked under it.
Hair care basics
How often should I wash my hair?
As often as your scalp needs it. An oily or flaky scalp usually does better with regular washing, while dry, curly and coily hair often needs fewer washes. In one large survey (funded by a shampoo maker, with very different age groups), people who washed more often reported less flaking and itch. In another study, itch and dandruff came back about a week after washing.
Are sulfates really bad for my hair?
Not bad in every case, but harsh ones are a poor choice for daily use. SLS is the standard irritant used as a control in skin patch tests, and a gentler cleanser (sodium lauroyl glutamate) irritated much less in a 15-person test. SLS can still be fine for an occasional deep clean. Our daily and curl shampoos use milder cleansers.
Are silicones bad?
No. Silicones cut friction, add shine and help with heat protection. The concern is build-up from water-insoluble types, and newer water-dispersible silicones are made to avoid that. In a lab test, a silicone also made hair straighten more evenly under a flat iron. If your hair feels coated, a periodic reset wash helps.
Is natural better than proven?
Proven is better, and natural does not mean gentle. In 62,354 patch-tested patients, 1.4% reacted to an essential oil alone, with ylang-ylang, sandalwood, jasmine and peppermint among the most common. That is why we look at studies, not at the word natural, and why our products have no essential oils.
Does biotin help hair?
Only if you are actually short of it, which is rare. A 2024 review found that biotin for hair is not supported by high-quality studies. High-dose biotin can also give wrong results on some blood tests, such as troponin tests. Tell your doctor if you take it.
Does rosemary oil work for hair?
It might, but the evidence is thin. The best-known trial compared it with minoxidil 2% in 100 men for 6 months, with no placebo group, and the groups did not differ. Only 8 non-prescription agents, rosemary oil included, have any investigator-blinded controlled trial. Rosemary can also cause allergic contact dermatitis in some people. For hair loss, talk to a doctor.
Do bond repair products really rebuild my hair?
Be careful with that wording. Hair strength comes from a balance of hydrogen, disulfide and ionic bonds, and the claim that a product rebuilds them is hard to check at home. What is shown in lab tests is smaller: panthenol and hydrolyzed proteins raised the force needed to break hair, in small studies. We call our products conditioners and masks, not repair treatments.
Does shampoo pH matter?
A little. In a review of 123 shampoos, 62% were above pH 5.5 and 81% of the anti-dandruff ones were. Alkaline conditions can make fibres swell, raise friction and roughen the cuticle, and bleached hair swells more at alkaline pH. That was a measurement study, not a trial of how hair looks after months of use, so treat it as a reason to choose a mild formula rather than a magic number.
Do I really need heat protection?
If you use hot tools, yes. In lab work, escaping steam made the cuticle bulge and crack, and the damage grew with each pass. Heat on wet hair did considerably more damage than heat on dry hair. Film-forming polymers cut breakage in a lab test. Use a heat protectant, keep the temperature down and avoid ironing wet hair.
What is hair porosity and does it matter?
Porosity describes how easily water gets in and out of the hair. Bleach nearly tripled the internal surface area of hair within the first minute, and repeated washing raised it too. In an industry study, coconut-oil pre-treatment limited that increase. Practical takeaway: damaged, porous hair likes a conditioner or mask, and a pre-wash oil can help before washing. Take the quiz for a routine that fits your hair.
Hair loss
What actually works for hair loss?
The best-studied options are prescription medicines, so talk to a doctor about them. In one 12-month trial of 450 men, hair improved in 80.5% on finasteride, 59% on minoxidil and 94.1% on both together. Among non-prescription products, only 8 agents have any investigator-blinded controlled trial. Cosmetics can support a routine but are not a replacement. Talk to a doctor if you want to explore your options.
Does minoxidil make you shed at first?
It can. In a 24-week study of 49 people, a temporary increase in shedding appeared in the first 12 weeks, and a bigger shed went with better results. It is not a reliable sign that the product is working, and it should settle. Take a baseline photo and talk to a doctor if shedding is heavy or lasts.
What happens if I stop using minoxidil?
The gains fade. In a controlled study of 36 men, a hair-weight gain of about 30% held while treated and was lost within 24 weeks of stopping. That study was small. Ask your doctor before you stop or change anything.
Why does minoxidil itch or irritate my scalp?
Itch and irritation are among the common complaints, and they were more common with 5% than with 2% in a 393-man trial. If it persists or spreads, stop and talk to a doctor, who can suggest other forms.
What are the side effects of finasteride?
In a meta-analysis of 15 placebo-controlled trials (4,495 men), finasteride 1 mg raised the risk of sexual dysfunction (relative risk 1.66). The label gives year-1 rates such as decreased libido 1.8% vs 1.3% on placebo. Reports of depression and of sexual problems that continued after stopping also exist. It is a prescription medicine, so talk to a doctor.
Is finasteride's sexual side effect partly in the mind (nocebo)?
Partly, and not entirely. In a blinded trial of 120 men, those told about sexual side effects reported them far more often (43.6% vs 15.3%). In a very large trial of 17,313 men, finasteride raised sexual dysfunction scores only slightly, and the gap shrank over time. Expectation adds to the effect, but the effect is real for some men. Talk to a doctor about your own risks.
Do regulators warn about finasteride and mood?
Yes. The UK regulator added a patient alert card in 2024, and the EU regulator confirmed suicidal thoughts as a side effect of finasteride tablets in 2025 (frequency unknown). If your mood changes on finasteride, stop and call your doctor. Do not decide alone: talk to a doctor.
Is rosemary oil as good as minoxidil?
It has not been shown to be. One 100-man trial compared rosemary oil with minoxidil 2% and had no placebo group; counts did not change at 3 months and both groups rose by 6 months. That is not enough to call them equal. Minoxidil is a medicine, so talk to a doctor about it.
Does microneedling work for hair loss?
Results are mixed. A 100-man trial of clinic microneedling plus minoxidil 5% beat minoxidil alone (count change 91.4 vs 22.2), but patients were not blinded. A 29-person home-device study found no statistically significant differences between groups. Microneedling alone showed no gain in density in a 30-person study. Common effects are redness and pain; use it clean and on intact skin only. Ask a doctor before combining it with a medicine.
Do hair supplements work?
Maybe a little, for some. A 2026 meta-analysis of 14 studies (967 people) found gains in growing-phase hair density and in pull-test results, but total hair count was not significant. Most trials are small and many are funded by the maker. There is not enough evidence to give iron to everyone with hair loss, so check with a doctor before you start.
When should I see a doctor about hair loss?
Sooner is better if you notice a widening part, a receding hairline, patches, pain, scalp sores or a sudden heavy shed. Women normally shed 50 to 150 hairs a day, and shedding without visible thinning often turns out to be early pattern loss (about 60% in one biopsy series). A doctor can look at the cause and discuss options.
Our products
What is in your formulas, and why?
Every key ingredient on a product page has a stated role and a link to the study behind it. The wash and care lines use mild cleansers, conditioning agents, panthenol, protein fragments and oils. The Density Scalp Serum uses caffeine, adenosine, niacinamide, panthenol and procyanidin B-2. The full ingredient list is shown on every page.
What doses did the studies use?
We print the dose from the study next to each active, and we say it is the studied dose, not a promise. For the serum: caffeine 0.2%, adenosine 0.75%, niacinamide 2%, panthenol 1% and procyanidin B-2 1% (a purified form, not whole apple extract). Some of these studies were funded by the maker or had no placebo, and we say so on the page.
Which products suit my hair type?
How long until I see results?
It depends on the product. Washes, conditioners and stylers work from the first use. The Scalp Shampoo is aimed at fewer flakes within about 4 weeks. Trials of hair-density products run for months: the Density Scalp Serum is a 4 to 6 month commitment, and its ingredient trials ran 6 to 12 months.
Could your products irritate my scalp?
Any product can, so patch test first: put a little on the inner arm or behind the ear and wait a day. We leave out the common culprits: added fragrance, essential oils and MI/MCI preservatives. In one study, linalool and limonene were the allergens most often listed on products. If you get a rash, burning or lasting itch, stop and talk to a doctor.
What do you leave out of your products?
Added fragrance, essential oils, MI and MCI preservatives, formaldehyde releasers, coal tar and, in daily products, harsh sulfates and drying alcohols. Each item on the avoid list has a reason and a study, and you can read the reasoning in our topics section. MI was banned in leave-on cosmetics in the EU from 2017.
How are you different from other brands?
We link the study for each key ingredient and print the dose next to it. We state weak points (small, no placebo, maker-funded). We say the time to results in months. We run no ads and no affiliate links, and there is no subscription. We also say plainly that our serum is a cosmetic. Read the comparison table on any product page.
Can the Density Scalp Serum regrow my hair?
No. It is a cosmetic, not a medicine, and it does not treat hair loss. Its ingredients have small, short studies: for example caffeine 0.2% matched minoxidil 5% in a 210-man trial that was open-label and maker-sponsored. For hair loss, talk to a doctor about proven options. The serum can sit next to that care, not replace it.
Are your reviews real?
Yes. We show only real reviews from real customers who agreed to have them shown. We never write, buy or edit reviews, and we never invent ratings or customer numbers. If a product has no reviews yet, we say so rather than fill the space.
Why does a free guide sell products?
Because the guides, quiz and encyclopedia are free and stand on their own. You get the same advice whether you buy or not, and nothing is gated. The guides cite studies, include honest negatives and name options that are not our products. We run no ads and no affiliate links, so our products are how the site pays for itself.
Orders and returns
Can I buy Hairmetry products?
How much is shipping, and when does it arrive?
Shipping is €4.95 in the Netherlands and Belgium, €9.95 in the rest of the EU, and free from €49. We ship orders placed before 21:00 from Monday to Saturday the same day. Delivery takes 1 working day in the Netherlands, 1-2 in Belgium, Luxembourg and Germany, 2-3 in France, Austria and Denmark, and 3-5 elsewhere in the EU. Your cart and checkout show the shipping cost before you pay.
Can I return an order?
Yes. You have 14 days from receiving your order to change your mind, without giving a reason. Read the full returns policy. We refund the goods and the standard shipping you paid within 14 days of getting your notice.
How do I start a return?
To send goods back, start a return: choose the items and you get the return address straight away. Return shipping costs are for you, and sealed hair and scalp products cannot be returned once the seal is broken.
What if my order arrives damaged or wrong?
Email to be added with a photo within a few days of delivery. We send a replacement or refund you, and we pay the return shipping in these cases. This is on top of the 14 days you have to change your mind.
Is paying safe?
Yes. You pay on a secure page run by our payment provider, and we never see or store your card or bank details. Your order is only processed after the payment succeeds. Prices include 21% VAT and you see the final total before you order.
Is there a subscription?
No. Every order is a one-off purchase and no subscription is created. You can come back whenever you like.
Do I need an account?
No. You can check out as a guest. We keep your order details only as long as needed to deliver and for our accounts, and we email you a confirmation. See the privacy notice.
Who do I contact if there is a problem with my order?
Email to be added and tell us what went wrong and your order number. We reply within a few working days. Our terms of sale list our company details.
What if my order is late?
We email you if an order will be late. If we have not delivered within 30 days of your order, you can cancel and get a refund. Contact to be added and we will sort it out.
This is not medical advice, just handy to know. Talk to a doctor if you want to explore an option further. Still stuck? Email [email protected] or use the contact form.