In Short
- Trichology is the study of the hair and scalp. It covers how hair is built, how it grows and the conditions that disturb it.
- Every hair has a visible shaft and a follicle below the skin. The follicle cycles through growth, transition and rest, and most hair loss disrupts that cycle.
- Pattern hair loss, alopecia areata, telogen effluvium, traction alopecia and scarring alopecias each affect the follicle in a different way.
- A cause is found through history, the pattern of loss, a scalp examination and, where needed, blood tests.
- Trichology is not itself an AHPRA-regulated health profession. Some trichologists may hold separate healthcare qualifications.
Trichology is the study of the hair and scalp, a field of hair science that covers how hair is built, how it grows and what disturbs it. Most people meet the word when hair loss sends them searching for answers. This guide from Hair and Skin Science explains the science behind hair health: what trichology is, how a hair is made, how the growth cycle works, what goes wrong in common types of hair loss and how a cause is found. Hair loss is common. In an Australian study, pattern hair loss affected 73.5% of men and 57% of women aged 80 and over (Gan & Sinclair, 2005).
What is trichology?
The word comes from the Greek trikhos, meaning hair. In the broadest sense, trichology is the science of the structure, function and diseases of the human hair. In a clinical sense, it is the diagnosis and treatment of disorders of the scalp and hair (Institute of Trichologists, n.d.).
It helps to separate the field from the job title. A trichologist is a practitioner trained in hair and scalp conditions. The Institute of Trichologists states that trichologists are not medically qualified, that they cannot prescribe, and that they work with a GP or dermatologist when medication or a biopsy is needed for a complete diagnosis (Institute of Trichologists, n.d.). In Australia, the Australian Health Practitioner Regulation Agency (AHPRA) regulates 16 health professions, and trichology is not one of them (AHPRA, n.d.). A doctor can diagnose the cause of hair loss and prescribe treatment where it is needed.
This guide explains the science of trichology. It is not a trichology service. Hair and Skin Science is a medical clinic, and our doctors and registered nurses are registered with AHPRA.
The science of hair: how a hair is built
Each hair has two parts: the shaft, which is the visible part above the skin, and the follicle, which sits below the surface. The shaft is a thin cylinder of non-living, keratinised cells. Most of its bulk is the cortex, which determines strength, texture and colour. Overlapping cuticle cells surround the cortex, and thicker hairs can also have a central medulla (Hoover et al., 2023).
The living work happens in the follicle. At its base, the hair bulb surrounds the dermal papilla, a cluster of cells with its own blood supply. The papilla is believed to be a primary orchestrator of hair growth, sending signals that set the size and colour of the hair shaft. The follicle’s outer root sheath also holds stem cells, which are thought to sit in a region called the bulge (Hoover et al., 2023).
Humans have roughly five million hair follicles, but most produce tiny, fine vellus hairs. The darker, thicker terminal hairs of the scalp, eyebrows and eyelashes are present from birth, and at puberty androgens convert some vellus hairs elsewhere on the body into terminal hairs (Hoover et al., 2023).
The hair growth cycle
Every follicle cycles through growth, transition and rest. The cycle matters because most hair loss is a disturbance of it (Hoover et al., 2023).
| Phase | What happens | How long it lasts |
|---|---|---|
| Anagen (growth) | The follicle is active and produces the hair fibre | Several years |
| Catagen (transition) | The follicle regresses and a club hair forms | A few weeks |
| Telogen (rest) | The follicle is dormant and no growth occurs | A few weeks to nearly a year for scalp hair |
Scalp hair grows about 0.35 mm a day, or roughly 1 cm a month, and around 100 to 200 hairs are shed each day. About 10 to 15% of hairs are in the resting phase at any time (Hoover et al., 2023). Some daily shedding is part of the cycle. Hair loss describes a slowing of growth, thinning, excessive shedding, or a failure to replace hairs that are lost.
What goes wrong: the science behind common types of hair loss
Most types of hair loss disrupt the cycle in a particular way, and the pattern tells a clinician where to look.
| Type | What is happening at the follicle | Usual pattern |
|---|---|---|
| Androgenetic alopecia (pattern hair loss) | Genetically sensitive follicles shrink, so each cycle makes a shorter, finer hair (Liu et al., 2025) | Temples and crown in men, a widening part in women (Bhat et al., 2020) |
| Telogen effluvium | Many follicles enter the resting phase together and shed together (Rebora, 2019) | Diffuse thinning, a few months after a trigger |
| Alopecia areata | The immune system interrupts growth without destroying the follicle (Pratt et al., 2017) | Smooth, round or oval bald patches |
| Traction alopecia | Repeated pulling from tight styles strains the follicle, and it can scar if the pulling continues (Billero & Miteva, 2018) | Front and sides of the hairline |
| Scarring alopecias | The follicle is damaged and replaced by scar tissue, so the loss is permanent (Hoover et al., 2023) | Shiny, bare patches of skin |
Other factors can sit behind these patterns or add to them, including thyroid disease, pregnancy and menopause, some medications, iron deficiency and major physical or emotional stress (Rebora, 2019; Bhat et al., 2020; Patel et al., 2013; Almohanna et al., 2019). More than one can be present at once. You can read more on our pages for alopecia, hair loss in men and hair loss in women.
How is hair loss diagnosed?
Diagnosis means working out which of those mechanisms is at play. The standard methods for hair and follicle disease are clinical inspection, observing the pattern of balding, a pull test, trichoscopy, biopsy and trichograms (Fernández-Domper et al., 2023). An assessment usually draws on:
- Your history. When the hair loss started, how quickly it is progressing, family history, recent illness, medications and hair practices.
- The pattern of loss. Where on the scalp it is happening, and whether it is patchy or diffuse.
- A scalp examination. This can include trichoscopy, a noninvasive office procedure that uses a handheld or digital dermatoscope to look at hair shafts, follicle openings and the skin around them (Fernández-Domper et al., 2023).
- Blood tests, where needed. These look for contributing factors such as iron deficiency and thyroid disease.
Some diagnoses are made by exclusion. Telogen effluvium has no specific trichoscopy finding, so it is diagnosed by ruling out other causes and should not rest on trichoscopy alone. In the acute form, hair loss becomes evident two to three months after the trigger. Telogen effluvium often improves after the trigger resolves, although recovery varies.
Careful assessment matters because similar-looking hair loss can have different causes. Exclamation point hairs, for example, can suggest alopecia areata, but they also occur in trichotillomania, a hair-pulling disorder, and can lead to a wrong diagnosis (Fernández-Domper et al., 2023). Healthdirect recommends talking to your doctor if you are worried about hair loss.
How Hair and Skin Science assesses hair loss
A consultation starts with understanding the cause. Assessment may include a medical history, scalp examination and, where appropriate, blood testing. We then discuss which options may be appropriate for you. Depending on the type of hair loss, options can include medical therapy prescribed by a doctor, PRP hair loss treatment, low-level laser therapy and, where hair loss is more advanced, hair transplantation. They are often combined.
Trichology FAQs
What is trichology?
Trichology is the study of the hair and scalp. It covers how hair is built and grows, and the diseases and disorders that affect the hair and scalp (Institute of Trichologists, n.d.).
Is a trichologist a doctor?
No. The Institute of Trichologists states that trichologists are not medically qualified, although they receive clinical training specific to the hair and scalp. They are not able to prescribe medication (Institute of Trichologists, n.d.).
What is hair made of?
The visible hair shaft is made of keratin, in a cortex surrounded by overlapping cuticle cells, with a central medulla in some thicker hairs (Hoover et al., 2023).
How much hair is normal to lose each day?
Around 100 to 200 hairs a day are shed as part of the normal cycle (Hoover et al., 2023). More hair than usual on the pillow, in the brush or in the shower drain is worth raising with a doctor.
Who should I see about hair loss?
A doctor is a sensible first step. Persistent or unexplained hair loss can occasionally be a sign of an underlying illness, so blood tests and a scalp assessment are worth arranging with your doctor or at a hair loss clinic.
Key Takeaways
- Trichology is the study of the hair and scalp. The word describes a field of science as well as a job title.
- Each hair is a shaft and a follicle, and the follicle cycles through growth, transition and rest. Most hair loss disturbs that cycle.
- Different types of hair loss affect the follicle in different ways, which is why the cause decides the treatment.
- A diagnosis draws on history, the pattern of loss, a scalp examination and, where needed, blood tests.
- Diagnosis and prescribed treatment sit with a doctor. Results vary and are not guaranteed.
To find out what is behind your hair loss, book a free consultation at one of our clinics across Australia. You can also read more about alopecia hair loss.
References
Almohanna HM, Ahmed AA, Tsatalis JP, Tosti A. The Role of Vitamins and Minerals in Hair Loss: A Review. Dermatol Ther (Heidelb). 2019;9(1):51-70. doi:10.1007/s13555-018-0278-6
Australian Health Practitioner Regulation Agency (AHPRA). What we do. https://ahpra.gov.au/about-ahpra/what-we-do.aspx. Accessed 15 October 2026.
Bhat YJ, Saqib NU, Latif I, Hassan I. Female Pattern Hair Loss: An Update. Indian Dermatol Online J. 2020;11(4):493-501. doi:10.4103/idoj.IDOJ_334_19
Billero V, Miteva M. Traction alopecia: the root of the problem. Clin Cosmet Investig Dermatol. 2018;11:149-159. doi:10.2147/CCID.S137296
Fernández-Domper L, Ballesteros-Redondo M, Vañó-Galván S. [Translated article] Trichoscopy: An Update. Actas Dermosifiliogr. 2023;114:T327-T333. doi:10.1016/j.ad.2023.02.006
Gan DC, Sinclair RD. Prevalence of male and female pattern hair loss in Maryborough. J Investig Dermatol Symp Proc. 2005;10(3):184-189. doi:10.1111/j.1087-0024.2005.10102.x
Hoover E, Alhajj M, Flores JL. Physiology, Hair. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated 2023 Jul 30. https://www.ncbi.nlm.nih.gov/books/NBK499948/
Institute of Trichologists. What is Trichology? https://trichologists.org.uk/what-is-trichology/. Accessed 15 October 2026.
Liu Y, Tosti A, Wang ECE, et al. Androgenetic alopecia. Nat Rev Dis Primers. 2025;11:73. doi:10.1038/s41572-025-00656-9
Patel M, Harrison S, Sinclair R. Drugs and hair loss. Dermatol Clin. 2013;31(1):67-73.
Pratt CH, King LE Jr, Messenger AG, Christiano AM, Sundberg JP. Alopecia areata. Nat Rev Dis Primers. 2017;3:17011. doi:10.1038/nrdp.2017.11
Rebora A. Telogen effluvium: a comprehensive review. Clin Cosmet Investig Dermatol. 2019;12:583-590. doi:10.2147/CCID.S200471
This page is general information only and does not substitute individual medical advice. Individual results vary and outcomes are not guaranteed. Any medical procedure carries risks. Seek an assessment from a qualified practitioner to determine whether a treatment is right for you.
