Lash science · The natural lash
Anatomy and the growth cycle
A lash is the visible end of a small organ. Under the skin of the lid there is a follicle, two glands, a web of nerves and a clock that runs for months. Everything a lash artist does sits on top of that.
The follicle
What is under the skin
The skin of the eyelid is the thinnest on the body, with only two layers where the scalp has three. A lash follicle roots in the deeper one, the dermis, which makes it shorter than a scalp follicle.1
Measured on tissue from ten patients, an upper-lid follicle is about 1.8 mm deep and a lower-lid follicle about half that. A later study put both nearer 1.9 mm and found the root meeting the skin at a slant of about 75 degrees. The samples are small and the two do not agree on the lower lid.35
Two things set a lash follicle apart. It has no muscle, so a lash cannot stand on end the way the hair on your arm does. And it is not driven by the hormones that thicken other body hair.17
A lash follicle at the edge of the lid, seen from the side. Choose a part.
The part you see. It rarely grows past 12 mm.1
1.8 mm
the depth of an upper-lid follicle
0.19 mm
the width of its bulb
75 degrees
the slant at which the root meets the skin
90 to 160
lashes on the upper lid
75 to 80
lashes on the lower lid
Before birth
when the number of follicles is set
That last number matters most. The follicles you are born with are the ones you have. A follicle that is destroyed is not replaced.17
At the atelier
This is why nothing we do pulls on the root. Extensions are bonded to the lash, never to the skin, and they come off with a remover that dissolves the bond. We do not tug, pick or cut.
Removal, in the libraryThe glands
Three glands keep the edge of the lid working
Each lash follicle has two glands that empty into it. The gland of Zeis makes sebum, an oil with lubricating and antimicrobial properties. The gland of Moll exists nowhere else on the body.18
What the gland of Moll is for is still not settled. Its secretion has been shown to contain lysozyme, antibodies and antimicrobial peptides, which points to defence, and a 2025 review says plainly that its function remains mostly guesswork.8910
Just behind the lash line, inside the lid, sit the meibomian glands. They make the oil that forms the outer layer of the tear film, a layer about 40 millionths of a millimetre thick.1112
At the atelier
The gland openings sit right at the lash line. It is the reason we keep adhesive off the skin and off the lid margin, and the reason a clean lash line matters more with extensions than without.
Attachment, in the library- Gland of Zeis
- An oil gland on the follicle. The whole cell breaks down to become the sebum.
- Gland of Moll
- Found only at the lid margin. Carries lysozyme, antibodies and antimicrobial peptides.
- Meibomian glands
- 24 to 40 in the upper lid, 20 to 30 in the lower. They make the oil of the tear film.
- In reserve
- About 300 micrograms of that oil in the lids, against about 10 spread on the eye.
- When one is infected
- A stye.
The three glands of the lid margin, from the published anatomy.
Touch
A lash is a touch sensor
The root of a human lash is wrapped in several kinds of nerve ending at once, in a pattern the anatomists who mapped it called unique to the lash.13
The accepted explanation is that they set off the blink. Touch a lash and the lid closes before you decide anything. That purpose is an inference, though a reasonable one. The reflex itself has been timed.1417
At the atelier
Weight on a lash is felt at its root. If a set feels heavy, it is heavy. Tell us, and we lighten it at the next fill.
Thickness and weight, in the libraryThe blink reflex, in thousandths of a second
Timed with a small electrical pulse to the nerve above the eye, the standard laboratory test. No study has timed a blink from the touch of a lash itself.
The cycle
The life of one lash
A lash grows, stops, rests, and falls. Then the follicle starts again. The three phases are called anagen, catagen and telogen.1
The most direct measurement comes from a study that photographed the same lashes every week for nine months. Growth lasted about 34 days at 0.12 mm a day, and the whole cycle about 90 days. Reviews quote longer spans, with growth of four to ten weeks inside a life of four to eleven months.21
Scalp hair runs on a different scale: it can grow for six or seven years, at 0.3 to 0.4 mm a day. A lash stays short because its growing phase is short.71
Day 12. Growing, about 0.12 mm a day.
Timed from the one study that followed lashes week by week: four women, nine months. Reviews give longer cycles.
At the atelier
An extension rides on a lash that has its own clock. Some lashes in every set are always near the end of theirs, which is why a set thins unevenly and why we fill every two to three weeks.
Retention and fills, in the libraryEvery lash is on its own clock.
On any day some are growing, some are resting, and one or two are about to fall.
Curl and colour
Curl and colour are decided in the bulb
Every natural lash is curved, in every person, and the curve begins in the bulb. Inside the follicle several building blocks are laid down unevenly from one side to the other, the same pattern found in curly scalp hair, where the curve has been shown to be programmed in the bulb.1215
The researchers who mapped it put it simply: structurally, a lash is very close to a curly hair. How strongly it lifts and curls varies from one person to the next, along with its thickness.26
Colour is set there too. Lashes turn grey far later than scalp hair and rarely go white. Their pigment cells carry an enzyme that scalp pigment cells lack, and that is the proposed reason. It has not been proven.421
Age changes them all the same. In 179 healthy women, upper lashes were shorter, finer and lighter in each older age group.16
At the atelier
We read your own curl before we choose one, and we measure again at every full set. A design that suited you ten years ago may need a lighter fibre now. That is biology, not damage.
Curl, in the libraryAverage length of the upper lashes, 179 women
Lashes also become finer and lighter with age. The study compared different women at one moment, not the same women over time.
Company
Who else lives on the lash line
A lash line is inhabited. It carries a normal community of bacteria that differs a good deal from person to person.25
It can also carry a mite. Demodex folliculorum is about a third of a millimetre long and lives at the root of the lash. It is part of the normal life of the lid, and many people who carry it never notice.2021
How common it is depends on who is asked. It rises with age, and it is far more common where the lid is already inflamed.222324
At the atelier
We clean the lash line before every appointment and show you how to wash it at home. Extensions do not excuse you from washing your lashes. They are the reason to.
Cleansers, in the libraryPeople carrying the mite, or its sign, in four studies
Four different groups and methods, so the bars show a pattern, not a trend line.
At the atelier
What the anatomy asks of a lash artist
A free 30-minute consultation comes first. We look at your natural lashes under magnification and draw the map before a single fibre is placed.
- The root
- nothing pulls on it
- The lid margin
- nothing is bonded to it
- The cycle
- a fill every two to three weeks
Sources
Every numbered line above comes from one of these. Where a claim is still a hypothesis, the text says so.
- 1The eyelash follicle features and anomalies: a reviewAumond and Bitton. Journal of Optometry, 2018.Review of the published research
- 2Human eyelash characterizationThibaut, De Becker, Caisey, Baras, Karatas, Jammayrac, Pisella and Bernard. British Journal of Dermatology, 2010.Measured: lid tissue from 17 patients; four women followed weekly for nine months
- 3Anatomy and physiology of eyelash follicles: relevance to lash ablation proceduresElder. Ophthalmic Plastic and Reconstructive Surgery, 1997.Measured: tissue from 10 patients
- 4Biology of the eyelash hair follicle: an enigma in plain sightPaus, Burgoa, Platt, Griffiths, Poblet and Izeta. British Journal of Dermatology, 2016.Review of the published research
- 5New insights into the anatomy of the eyelashes with regard to ethnic differences against a clinical backgroundSingh, Hammer and Paulsen. Ophthalmic Plastic and Reconstructive Surgery, 2024.One small study: eight lids
- 6Ethnic characteristics of eyelashes: a comparative analysis in Asian and Caucasian femalesNa, Kwon, Kim, Park, Oh, Kim, Cho and Eun. British Journal of Dermatology, 2006.Measured: 4,661 lashes on 30 women
- 7Enhanced eyelashes: prescription and over-the-counter optionsJones. Aesthetic Plastic Surgery, 2011.Review; used here for cycle biology only
- 8Human glands of Moll: histochemical and ultrastructural characterizationStoeckelhuber, Stoeckelhuber and Welsch. Journal of Investigative Dermatology, 2003.Measured on human lids
- 9Immunolocalization of defensins and cathelicidin in human glands of MollStoeckelhuber, Messmer, Schubert, Stoeckelhuber, Koehler, Welsch and Bals. Annals of Anatomy, 2008.Measured on human lids
- 10Glands of Moll: history, current knowledge and their role in ocular surface homeostasis and diseaseStopfer, Zahn, Jüngert, Aumüller, Moll, Schicht, Makarenkova, de Paiva and Paulsen. Progress in Retinal and Eye Research, 2025.Review of the published research
- 11TFOS DEWS II tear film reportWillcox, Argüeso, Georgiev and colleagues. The Ocular Surface, 2017.International consensus report
- 12Comprehensive assessment of the meibomian glands by meibography: why the upper eyelids matterGupta and Karpecki. Cornea, 2025.Review of the published research
- 13The sensorineural apparatus of the human eyelidMunger and Halata. American Journal of Anatomy, 1984.Measured: microscopy of human lids
- 14The blink reflex and its modulation, part 1: physiological mechanismsKofler, Hallett, Iannetti, Versace, Ellrich, Téllez and Valls-Solé. Clinical Neurophysiology, 2024.Review of the published research
- 15Human hair shape is programmed from the bulbThibaut, Gaillard, Bouhanna, Cannell and Bernard. British Journal of Dermatology, 2005.Measured on scalp follicles; applied to lashes by analogy
- 16Epidemiologic analysis of change in eyelash characteristics with increasing age in a population of healthy womenGlaser, Jones, Carruthers, Campo, Moench, Tardie, Largent and Caulkins. Dermatologic Surgery, 2014.Measured: 179 women, photographs
- 17TFOS Lifestyle: impact of cosmetics on the ocular surfaceSullivan, da Costa, Del Duca and colleagues. The Ocular Surface, 2023.International consensus report
- 18Effect of repeated epilation for minor trachomatous trichiasis on lash burden, phenotype and surgical management willingnessHabtamu, Wondie, Gobezie and colleagues. PLoS Neglected Tropical Diseases, 2020.Measured: 170 adults, scarred lids
- 19An experimental study to compare methods of eyelash ablationBartley, Bullock, Olsen and Lutz. Ophthalmology, 1987.Animal study: rabbits
- 20Demodex blepharitis: a comprehensive review of the disease, current management, and emerging therapiesRhee, Yeu, Barnett and colleagues. Eye and Contact Lens, 2023.Review; several authors tied to a drug maker
- 21Tea tree oil for Demodex blepharitisSavla, Le and Pucker. Cochrane Database of Systematic Reviews, 2020.Systematic review
- 22The prevalence of ocular Demodex folliculorum in 2253 young malesYe, Yan, Wang and Chen. Scientific Reports, 2022.Measured: 2,253 men
- 23Prevalence of Demodex folliculorum and Demodex brevis in patients with blepharitis and chalazionAkkucuk, Kaya, Aslan, Ozdemir and Uslu. International Ophthalmology, 2023.Measured: 530 people
- 24The prevalence of Demodex blepharitis in US eye care clinic patients as determined by collarettesTrattler, Karpecki, Rapoport, Sadri, Schachter, Whitley and Yeu. Clinical Ophthalmology, 2022.Measured: 1,032 clinic patients; industry-linked authors
- 25Comparative ocular microbial communities in humans with and without blepharitisLee, Oh, Jung, Kim and Jeon. Investigative Ophthalmology and Visual Science, 2012.One small study: 11 people
Lash science
The natural lash