Resource

Hair Loss Glossary

The terms you will meet in guides, on labels and at the dermatologist's office, explained in plain English.

2

2dDR: 2-deoxy-D-ribose: a sugar compound used in some FOLIGAIN® cosmetic products.

5

5-alpha reductase: The enzyme that converts testosterone into DHT. Finasteride and dutasteride block it.

A

Acne keloidalis nuchae: Firm bumps and scarring at the back of the neck, most common in men with curly hair.
Active ingredient: The component of a drug responsible for its effect, listed first on US Drug Facts labels.
Adrenal glands: Small glands above the kidneys that make hormones, including some androgens.
Alopecia: The medical term for hair loss of any kind.
Alopecia areata: An autoimmune condition that causes smooth, round patches of hair loss. It needs assessment by a dermatologist.
Alopecia totalis: Loss of all scalp hair, a form of alopecia areata.
Alopecia universalis: Loss of all hair on the scalp and body, the most extensive form of alopecia areata.
Amino acids: The building blocks of proteins, including keratin.
Anagen: The active growth phase of the hair cycle. On the scalp it lasts roughly 2–7 years.
Anagen effluvium: Rapid hair loss during the growth phase, most commonly caused by chemotherapy.
Androgen receptor: A protein in cells that responds to androgens such as DHT; its sensitivity is largely inherited.
Androgenetic alopecia: Pattern hair loss in men and women, driven by genetics and follicle sensitivity to androgens. The most common type of hair loss.
Androgens: Hormones such as testosterone and DHT that influence hair follicles, especially in pattern hair loss.
Anemia: A low red blood cell count, often from low iron, which can contribute to shedding.
Anti-androgen: A medicine that blocks the effects of male hormones, such as spironolactone.
Antifungal: An ingredient that controls fungi or yeast, such as ketoconazole.
Apoptosis: Programmed cell death; it drives the catagen phase of the hair cycle.
Arrector pili: The tiny muscle attached to each follicle that makes hair stand up (goosebumps).
Autoimmune: When the immune system mistakenly attacks the body's own tissue, as in alopecia areata.

B

Baricitinib: An oral JAK inhibitor approved in the US for severe alopecia areata.
Beard minoxidil: Off-label use of topical minoxidil to fill in facial hair.
Bioavailability: How much of a substance reaches the bloodstream or target tissue.
Biopsy (scalp): Removing a tiny piece of scalp to examine under a microscope and confirm a diagnosis.
Biotin: A B vitamin involved in keratin production. True deficiency is rare, and high doses can interfere with some lab tests.
Blood panel: A set of blood tests; for hair loss it often includes iron, thyroid and vitamin D.
Bulb: The rounded base of the hair root, where new hair cells are made.
Bulge: The part of the follicle that holds stem cells for new hair growth.

C

Caffeine (topical): A cosmetic ingredient studied for effects on hair follicles.
Carrier oil: A plain oil such as jojoba used to dilute essential oils.
Catagen: A short transition phase of 2–3 weeks between growth and rest, when the follicle regresses.
Central centrifugal cicatricial alopecia (CCCA): A scarring hair loss starting at the crown, most common in women of African descent.
Chemical damage: Weakening of hair from bleach, relaxers or perms.
Chemotherapy-induced alopecia: Hair loss caused by cancer drugs, usually temporary.
Cicatricial alopecia: Another name for scarring alopecia, where follicles are permanently destroyed.
Clinical trial: A controlled study in people testing whether a treatment works and is safe.
Club hair: A resting hair with a small white bulb at the root. It is the normal appearance of a shed telogen hair.
Collagen: A structural protein sold as a supplement; not proven for hair growth.
Compounded medication: A medicine custom-mixed by a pharmacy, not individually FDA-approved.
Conditioner: A product that smooths the hair cuticle and reduces breakage.
Contact dermatitis: An itchy rash caused by irritation or allergy to something touching the skin.
Cortex: The middle layer of the hair shaft, which gives hair strength and color.
Corticosteroid: An anti-inflammatory medicine, used as injections, creams or foams for some hair conditions.
Cosmetic claim: A claim about appearance (e.g. fuller-looking hair), not about treating a disease.
Crown: The top-back of the head, where many men first notice thinning.
Crown (vertex): The top back of the scalp, where hair naturally swirls. It is a common area for pattern thinning.
Cuticle: The outer protective layer of overlapping cells on a hair shaft.

D

DailyMed: The US National Library of Medicine database of official drug labels.
Dandruff: Flaking of the scalp, often linked to Malassezia yeast.
Density: The number of hairs per area of scalp. Thinning reduces visible density.
Dermal papilla: The cluster of cells at the base of the follicle that regulates hair growth.
Dermal sheath: The layer of tissue surrounding the hair follicle.
Dermatologist: A doctor specializing in skin, hair and nails.
Dermoscopy: Examining skin or scalp through a magnifying lens with light.
DHT (dihydrotestosterone): A potent androgen made from testosterone by 5-alpha reductase. It drives follicle miniaturization in susceptible people.
Diffuse thinning: Thinning spread evenly across the scalp rather than in patches.
Donor area: The back and sides of the head, where hair for transplants is taken.
Drug Facts label: The standardized label required on US over-the-counter drugs.
Dry scalp: Tight, flaky skin from lack of moisture, different from dandruff.
Dutasteride: A prescription drug that blocks both types of 5-alpha reductase; used off-label for hair loss.

E

Effluvium: A general term for excessive shedding.
Emollient: An ingredient that softens and smooths skin or hair.
Epidermis: The outermost layer of skin.
Estrogen: A hormone that helps keep hair in its growth phase; drops after pregnancy and menopause.
Ethanol: Alcohol used as a solvent in liquid minoxidil; can dry the scalp.
Excipient: An inactive ingredient in a medicine.
Exclamation-mark hairs: Short broken hairs narrower at the base, typical of alopecia areata.
Exogen: The release of the old hair from the follicle, often described as a separate part of the resting phase.

F

FDA: The US Food and Drug Administration, which regulates drugs and cosmetics.
Female pattern hair loss: Hereditary thinning in women, often a widening part.
Ferritin: A blood marker of stored iron, often checked when investigating hair shedding.
Finasteride: A prescription medicine that reduces DHT, used for male pattern hair loss under medical supervision.
Foam (Minoxidil): A Minoxidil format that dries quickly and usually contains no propylene glycol.
Follicle: The small pocket in the skin from which a hair grows.
Follicular unit: A natural group of 1–4 hairs growing together.
Folliculitis: Inflamed or infected hair follicles, seen as small red bumps.
Folliculitis decalvans: A scarring hair loss with pustules and inflammation.
Frontal fibrosing alopecia: A scarring hair loss that pushes the hairline back, often in postmenopausal women.
Frontal hairline: The front edge of the scalp hair.
FUE: Follicular unit extraction: a transplant method taking grafts one by one.
FUT: Follicular unit transplantation: a transplant method using a strip of scalp.

G

Genetics: Inherited traits; the main factor in pattern hair loss.
GHK-Cu: A copper peptide used in some cosmetic scalp serums.
Graft: A small piece of tissue containing hair follicles moved during a transplant.

H

Hair breakage: Hair snapping along the shaft rather than falling out at the root.
Hair count: The number of hairs in a set area, used to measure results in studies.
Hair cycle: The repeating stages of growth, regression, rest and shedding.
Hair diameter: The thickness of individual hairs; shrinks with miniaturization.
Hair fiber: Another term for the visible hair shaft.
Hair pull test: A gentle tug on a group of hairs to see how many come out.
Hair serum: A leave-on liquid product for the scalp or hair.
Hair shaft: The visible part of the hair above the skin. It is made mainly of the protein keratin.
Hair system: A non-surgical hairpiece attached to the scalp.
Hairline lowering: Surgery to move the hairline forward, mostly for women with high foreheads.
Heat damage: Weakening of hair from styling tools.
Hormonal hair loss: Hair loss driven by hormones, such as androgens or thyroid changes.
Hyperandrogenism: Higher-than-normal androgen levels, as can occur in PCOS.
Hyperthyroidism: An overactive thyroid; can cause diffuse shedding.
Hypertrichosis: Unwanted hair growth outside the treated area, such as on the face. It is a reported Minoxidil side effect.
Hypothyroidism: An underactive thyroid; can cause dry, thinning hair.

I

Inactive ingredients: Components that help deliver the active ingredient, like propylene glycol.
Inflammation: The body's response to irritation or injury, showing as redness or swelling.
Iron deficiency: Low body iron stores, a common and treatable cause of shedding.

J

JAK inhibitor: A class of drugs that calm certain immune signals, used for severe alopecia areata.

K

Keratin: The structural protein that makes up hair, skin and nails.
Ketoconazole: An antifungal used in dandruff shampoos, sometimes added to hair-loss routines.

L

Lichen planopilaris: An inflammatory scarring hair loss with redness around follicles.
Low-level laser therapy (LLLT): Red-light devices such as caps and combs cleared by the FDA for hair growth.
Ludwig scale: A three-stage scale used to grade female pattern hair loss by part width and density on top.

M

Malassezia: A yeast naturally on the scalp that can trigger dandruff.
Male pattern hair loss: Hereditary thinning in men, usually at the temples and crown.
Marine protein: A fish-derived supplement ingredient found in some hair products.
Medulla: The soft innermost core of some thicker hairs.
Melanin: The pigment that gives hair its color.
Menopause: The end of menstrual periods; hormonal changes can thin hair.
Microneedling: Creating tiny punctures in the scalp with a roller or pen to stimulate repair.
Miniaturization: The gradual shrinking of hair follicles in pattern hair loss, producing finer, shorter hairs.
Minoxidil: A topical active ingredient approved over the counter in the US for pattern hair loss, usually at 2% or 5%.
Minoxidil foam: A propylene-glycol-free version of topical minoxidil.
Minoxidil solution: The liquid form of topical minoxidil, usually applied with a dropper.
Moisturizer: A product that adds or holds water in skin or hair.

N

Nanoxidil®: A cosmetic ingredient used by DS Laboratories; not the same as minoxidil.
NDC: National Drug Code: a unique US identifier for each drug product.
Niacinamide: Vitamin B3, used in calming scalp serums.
Norwood scale: A seven-stage scale (Hamilton-Norwood) describing male pattern hair loss at the temples and crown.
Nutritional deficiency: Lacking a nutrient such as iron, zinc or vitamin D.

O

Off-label: Using an approved drug for a purpose not listed on its label.
Oily scalp: A scalp producing a lot of sebum, which can feel greasy.
Oral minoxidil: Low-dose minoxidil tablets prescribed off-label for hair loss.
OTC (over the counter): Medicines sold without a prescription.

P

Patch test: Trying a product on a small area first to check for irritation.
Patchy hair loss: Hair loss in distinct round or irregular areas.
PCOS: Polycystic ovary syndrome: a hormonal condition that can cause thinning scalp hair.
Peptide: A short chain of amino acids, used in some cosmetic hair products.
Perifollicular: Around the hair follicle.
pH: A measure of acidity; scalp and hair prefer slightly acidic products.
Placebo: An inactive treatment used for comparison in trials.
Porosity: How easily hair absorbs and holds moisture.
Postpartum shedding: Heavy shedding a few months after giving birth, usually temporary.
Potassium channel opener: A drug type, including minoxidil, that affects cell potassium flow.
Propylene glycol: A solvent used in many Minoxidil solutions. Some people find it irritating.
PRP (platelet-rich plasma): Injections of your own concentrated blood platelets into the scalp.
Psoriasis (scalp): An immune skin condition causing thick, silvery scales.
Pumpkin seed oil: A seed oil studied in one small trial for male pattern hair loss.

R

Receding hairline: A hairline moving backward, often at the temples.
Recipient area: Where grafts are placed during a hair transplant.
Regrowth: New hair growing where thinning had occurred.
Ritlecitinib: An oral JAK inhibitor approved in the US for severe alopecia areata from age 12.
Rosemary oil: A botanical oil studied in a small trial for hair loss.

S

Salicylic acid: An exfoliant used in shampoos to lift flakes.
Saw palmetto: A botanical extract sometimes used as a mild DHT blocker.
Scalp: The skin covering the top of the head.
Scalp massage: Rubbing the scalp to relax and possibly improve circulation.
Scalp micropigmentation: Tattooing tiny dots to mimic hair stubble or density.
Scalp scrub: An exfoliating product for removing buildup.
Scarring alopecia: A group of rare inflammatory conditions that permanently destroy follicles. Early diagnosis matters.
Sebaceous gland: The oil gland attached to each hair follicle.
Seborrheic dermatitis: A common scalp condition causing flaking, redness and itching, often called dandruff in its mild form.
Sebum: The natural oil produced by the scalp's sebaceous glands.
Sensitive scalp: A scalp that easily stings, itches or burns.
Shampoo: A cleanser for hair and scalp.
Shedding: The normal loss of hairs at the end of their cycle; 50–100 a day is typical.
Shedding phase: A temporary increase in shedding in the first weeks of Minoxidil, as resting hairs are replaced.
Side effect: An unwanted effect of a treatment.
Spironolactone: A prescription anti-androgen used off-label for female hair loss.
Split ends: Fraying at the ends of hair shafts.
Stem cells: Cells in the follicle bulge that regenerate hair.
Stress shedding: Everyday name for telogen effluvium after illness, stress or surgery.
Subscription: Automatic recurring product delivery, common with online hair-loss brands.
Sulfate-free: Shampoos without harsh sulfate cleansers, often gentler.
Supplement: A product taken by mouth to add nutrients; not FDA-approved like drugs.
Surfactant: The cleansing ingredient in shampoos.

T

Tea tree oil: A plant oil with mild antifungal action, used for dandruff.
Telehealth: Online doctor consultations, used by some hair-loss brands.
Telogen: The resting phase of the hair cycle, lasting about three months before the hair is shed.
Telogen effluvium: Diffuse, temporary shedding that starts 2–4 months after a trigger such as illness, childbirth or stress.
Temples: The sides of the forehead; recession here is an early male pattern sign.
Terminal hair: Thick, pigmented, fully developed hair, as opposed to fine vellus hair.
Testosterone: The main male hormone, converted to DHT in the body.
Thyroid: A gland in the neck controlling metabolism; imbalances affect hair.
Tinea capitis: A fungal scalp infection (scalp ringworm), common in children.
Topical: Applied to the skin or scalp.
Topical finasteride: Finasteride in a scalp spray or solution, usually compounded.
Traction alopecia: Hair loss caused by repeated pulling from tight hairstyles, extensions or headwear.
Transplant: Surgery moving follicles from the donor area to thinning areas.
Trichodynia: A burning or painful sensation of the scalp.
Trichologist: A hair and scalp specialist; not a medical doctor in the US.
Trichology: The study of hair and scalp health.
Trichorrhexis nodosa: Weak points along the hair shaft causing breakage.
Trichoscopy: Magnified examination of the scalp and hair that clinicians use to assess hair loss.
Trichotillomania: A condition involving the urge to pull out one's own hair.
TRIOXIDIL®: FOLIGAIN®'s proprietary cosmetic complex, used in selected FOLIGAIN® products to support the look and feel of thinning hair.

U

Unisex: Suitable for both men and women.

V

Vehicle: The base that carries an active ingredient (e.g. liquid or foam).
Vellus hair: Very fine, short, lightly pigmented hair. Miniaturized follicles can come to produce vellus-like hairs.
Vertex: Medical term for the crown.
Vitamin D: A vitamin involved in the hair cycle; low levels are linked with hair loss.
Volumizing: Cosmetic products that make hair look fuller.

W

Widening part: A part line that gets broader over time, a common sign in women.
Wig: A full hairpiece worn over the head.

Z

Zinc: A mineral needed for hair growth; zinc pyrithione treats dandruff.
Zinc pyrithione: An antifungal ingredient in many dandruff shampoos.

Important

This content is for educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease. Speak with a qualified healthcare professional about your individual situation.