Hair Library
Short answers to the questions people ask about hair terms, from anagen to widow’s peak. Each answer links to the full entry when there is more to know.
Alopecia areata is an autoimmune condition that can cause round patches of hair loss in the eyebrows, beard or scalp. Hair often regrows within a few months and may look white or grey at first before the natural colour returns.
Full entry: Do Eyebrows Grow Back? →Anagen is the growing phase of the hair cycle. For scalp hair it lasts 2 to 6 years according to a Deutsches Ärzteblatt review, and 2 to 7 years according to Cleveland Clinic.
Full entry: How Fast Hair Grows →Androgenetic alopecia, or pattern baldness, is the pattern hair loss behind most male and female thinning. It is primarily driven by genetic predisposition and sensitivity to androgen hormones.
Full entry: DHT and Hair Loss →Catagen is the short transition phase of the hair cycle, lasting about 1 to 2 weeks. Cell division stops and about two thirds of the lower follicle breaks down, while the dermal papilla stays intact and moves upward.
Full entry: How Fast Hair Grows →The Choi implanter pen is a hollow needle that places each graft at the planned angle, depth and direction. A Choi pen hair transplant is DHI done with this pen.
Full entry: DHI Hair Transplant →The crown, also called the vertex, is the highest point at the back of the head, where hair grows out in a spiral. Crown and vertex are two names for the same area.
Full entry: Crown Balding →The dermal papilla is a cluster of cells at the centre of the hair bulb. It signals the bulb and helps decide how thick, how long and what colour each hair grows.
Full entry: Hair Bulb Anatomy →DHI (Direct Hair Implantation) is a hair transplant in which each graft, extracted with the FUE method, is loaded into a Choi implanter pen and placed directly into the scalp without pre-opened channels. It is an implantation technique, not a separate extraction method.
Full entry: DHI Hair Transplant →Dihydrotestosterone (DHT) is a potent androgen that the body makes from testosterone using an enzyme called 5-alpha reductase. In people who are genetically sensitive to it, DHT makes hair follicles shrink.
Full entry: DHT and Hair Loss →The donor area is the back and sides of the head, where follicles resist DHT. An extracted follicle does not grow back in that spot, so extractions are spread out, and the donor supply is the limit of every plan.
Full entry: How Many Grafts Do I Need? →Finasteride blocks the enzyme that turns testosterone into DHT, the hormone that shrinks follicles in male pattern hair loss. It is a prescription medicine with possible side effects, so it should be started and followed by a doctor.
Full entry: Post-Finasteride Syndrome →Folliculitis is inflammation of the hair follicles. It often looks like a sudden acne breakout; each spot may have a red ring, and the skin can itch or feel painful.
Full entry: Scalp Pain and Hair Loss →FUE (Follicular Unit Extraction) moves hair follicles one by one from the back and sides of the scalp to thinning areas, without the linear scar of the older strip method.
Full entry: FUE Hair Transplant →In FUT, a thin strip of skin is removed from the back of the head, divided into grafts of 1 to 4 hairs, and the wound is closed with stitches. It leaves a line scar, while FUE leaves tiny dots.
Full entry: FUE vs DHI →A graft is a follicular unit taken from the donor area and placed in the thinning area. It holds one to four hairs, rarely more, so 2,000 grafts is roughly 3,600 to 4,600 hairs.
Full entry: How Many Grafts Do I Need? →The hair bulb is the rounded base of a hair root, deep inside the follicle, where living cells divide to build new hair.
Full entry: Hair Bulb Anatomy →The cortex is the thick middle layer of the hair shaft and makes up most of the hair. It also holds the melanin granules that give hair its natural colour, so dyes and bleach have to reach it to change the shade.
Full entry: Hair Shaft Anatomy →The cuticle is the overlapping outer layer of the hair strand, the layer you touch. It decides hair porosity: when its scales lie flat and tight, water struggles to get in.
Full entry: Hair Shaft Anatomy →The medulla is the soft core that runs down the centre of some hairs. It is the least understood of the three layers, and not every hair has one.
Full entry: Hair Shaft Anatomy →Hair porosity is how easily water gets into your hair and how well it stays there. It depends on whether the cuticle scales on each strand lie flat and closed or are raised and open, and it is independent of curl pattern.
Full entry: Hair Porosity →The hair shaft is the visible part of a hair above the skin, made of keratin in three layers: the cuticle, the cortex and, in thicker hairs, a central medulla. It forms in the follicle and cannot repair itself after it leaves the scalp.
Full entry: Hair Shaft Anatomy →Hair type describes the shape of the strand. The chart runs through 12 patterns, from 1A straight to 4C coily, and type is independent of porosity.
Full entry: Hair Type Chart (1A–4C) →A hybrid plan shaves only a specific area, usually the donor area or a small recipient zone, while the rest of the hair stays long. It allows more grafts than a fully unshaven session.
Full entry: No-Shave Hair Transplant →Hair follicle unit: see graft
Ketoconazole is an antifungal medicine sold as a shampoo. It is fungicidal, blocking the ergosterol that scalp yeast needs for its cell membrane.
Full entry: Ketoconazole Shampoo →LLLT: see red light therapy for hair
Matrix cells are fast-dividing cells that surround the dermal papilla in the hair bulb and turn into the hair shaft.
Full entry: Hair Bulb Anatomy →A mature hairline is the slightly higher, more shaped hairline most men develop as they move from their teens into adulthood. It is a change in shape, not a loss of density.
Full entry: Mature Hairline →Melanocytes are pigment cells that live among the matrix cells of the hair bulb. They make less melanin over time, and age-related graying cannot be stopped.
Full entry: Gray Hair: Causes →Minoxidil is an established medication for certain types of hair loss. It is a drug, not a hair oil, and the FDA-approved label says not to use it for sudden or patchy hair loss.
Full entry planned: MinoxidilIn an unshaven hair transplant, often called U-FUE, neither the donor area nor the recipient area is completely shaved before surgery.
Full entry: No-Shave Hair Transplant →The Norwood scale is the classification most doctors use for male pattern hair loss. It describes the usual ways the loss moves, stage by stage, from Norwood 1 to Norwood 7.
Full entry: Norwood Scale: Stages 1–7 →A pilar cyst, also called a trichilemmal cyst, is a keratin-filled cyst that starts in the outer root sheath of a hair follicle. DermNet says about 90% are found on the scalp.
Full entry: Bumps on the Scalp →Post-finasteride syndrome is a term for sexual, neuropsychiatric and physical symptoms that persist for at least three months after a man stops finasteride. A 2020 review concluded that studies so far can neither confirm nor refute it as a distinct disease.
Full entry: Post-Finasteride Syndrome →Postpartum hair loss is heavier-than-normal shedding after giving birth, medically termed postpartum telogen effluvium. It is considered a normal response to hormonal change, not a disease.
Full entry: Postpartum Hair Loss →PFS: see post-finasteride syndrome
Pattern baldness: see androgenetic alopecia
Papilla: see dermal papilla
Red light therapy, or low-level light therapy (LLLT), is a non-invasive option for pattern hair loss. Clinical studies suggest it may improve hair density, but research does not prove it is consistently more effective than minoxidil.
Full entry: Red Light Therapy →Sapphire FUE is a FUE hair transplant in which the recipient channels are opened with sapphire blades instead of steel. The smaller, cleaner channels usually mean less tissue trauma, faster crusting and closer graft placement.
Full entry: Sapphire FUE →Seborrheic dermatitis causes an itchy, flaky, scaly rash on oily areas such as the scalp. It is the Malassezia-linked condition most people mean by a scalp yeast infection.
Full entry: Scalp Yeast Infection →Shock loss is a temporary shedding phase after a hair transplant, triggered by surgical stress to the scalp and typically starting 2 to 4 weeks after the procedure. The follicles remain healthy beneath the skin, and new growth resumes within 4 to 6 months.
Full entry: Shock Loss →Spironolactone is a prescription water tablet that dermatologists use off-label for women with female pattern hair loss, because it blocks the effect of androgen hormones on the hair follicle.
Full entry: Spironolactone for Hair Loss →Strip method: see FUT (the strip method)
Telogen effluvium is sudden diffuse shedding that follows illness, childbirth or stress. Shedding usually starts two to three months after the trigger, and it is usually self-limiting once the trigger is removed.
Full entry planned: Telogen EffluviumTelogen is the resting phase of the hair cycle. It lasts 2 to 4 months according to a Deutsches Ärzteblatt review, and up to 4 months according to Cleveland Clinic.
Full entry: How Fast Hair Grows →Terminal hair is thick and pigmented, over 60 micrometres wide and longer than 2 centimetres. It grows on the scalp, eyebrows, armpits, beard and pubic region.
Full entry: How Many Hairs Are on the Head →Trichodynia is pain, burning, tingling or soreness of the scalp in people who are losing hair. It is common in telogen effluvium and pattern hair loss.
Full entry: Scalp Pain and Hair Loss →Trichorrhexis nodosa is a common hair shaft problem in which thickened or weak points, called nodes, form along the shaft and make the hair break off easily. It can be inherited or triggered by blow-drying, ironing, over-brushing, perming or heavy chemical use.
Full entry: Hair Shaft Anatomy →Type 1 hair is naturally straight, staying flat whether air-dried or styled. It grows from round follicles and reflects light easily.
Full entry: Type 1 Hair: Straight (1A–1C) →U-FUE: see no-shave (unshaven) FUE
Vellus hair is the fine, short, pale hair that covers most of the body. It is under 30 micrometres wide and under 2 millimetres long.
Full entry: How Many Hairs Are on the Head →Vertex: see crown (vertex)
A widow’s peak is a natural hairline shape in which the centre dips lower than the rest of the hairline, forming a V in the middle of the forehead.
Full entry: Widow’s Peak Hair Transplant →Talk to our hair team on a free video call, in your language. You receive a written plan with your technique, estimated grafts and all-inclusive price. If a hair transplant isn't right for you, we tell you honestly.
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