7.2 Hair Growth Cycles, Loss & Hair Analysis
Key Takeaways
- The anagen (growth) phase lasts roughly 3 to 5 years and about 90% of scalp hair is in this phase at any time
- Catagen is a brief transition phase of a few weeks; telogen is the resting phase lasting about 3 months, after which the hair sheds
- Hair grows an average of about one-half inch (1.25 cm) per month, and normal daily shedding is about 35 to 40 hairs (sources cite up to 100)
- Androgenetic alopecia is hereditary pattern hair loss; alopecia areata is sudden patchy loss requiring medical referral; traction alopecia is caused by prolonged tension such as tight braiding
- Porosity, elasticity, texture, and density analysis before a chemical service determines product choice, processing time, and expected results
Hair Growth Cycles, Loss & Hair Analysis
The written exam treats hair growth as a clock: every follicle on the scalp cycles independently through three phases, and questions test the name, length, and percentage of hair in each one. Hair loss questions then build on that clock — each type of alopecia (the technical term for hair loss) is defined by what disrupts the cycle. Finally, hair analysis questions test whether you can translate an observed condition into a safe service decision.
The Three Growth Phases
| Phase | What Happens | Typical Duration | % of Scalp Hair |
|---|---|---|---|
| Anagen | Active growth; new cells form in the bulb and the strand lengthens | About 3 to 5 years (can range 2-6) | ~90% |
| Catagen | Transition; cell division stops and the follicle shrinks toward the surface | A few weeks (about 1-2 weeks) | ~1% |
| Telogen | Resting; the fully formed hair rests in the follicle, then sheds or is pushed out by a new anagen hair | About 3 months | ~10% |
The most-tested facts here: anagen is the growth phase and the longest; about 90% of hair is in anagen and about 10% in telogen at any moment; catagen is the shortest phase. Because each follicle cycles on its own schedule, shedding is spread out instead of all at once. On average, scalp hair grows about one-half inch per month (roughly 6 inches per year), faster in summer than in winter and faster during the day than at night. Normal daily shedding is commonly cited as 35 to 40 hairs per day in textbooks (some sources say up to 100); either figure represents a healthy follicle recycling, not hair loss.
Types of Hair Loss (Alopecia)
The exam expects you to match each loss pattern to its name and cause, and to know which ones are beyond the cosmetologist's scope:
| Type | Pattern & Cause | Key Exam Note |
|---|---|---|
| Androgenetic alopecia | Hereditary pattern thinning; receding hairline/crown in men, general thinning over the crown in women | The most common form of hair loss; not a disease; salon services can camouflage but not cure |
| Alopecia areata | Sudden loss in round or irregular patches, with no scaling or broken skin | Autoimmune in nature; refer the client to a physician |
| Postpartum alopecia | Temporary shedding at the end of pregnancy as hormonal shifts push many hairs into telogen at once | Usually self-correcting within about a year |
| Telogen effluvium | Diffuse shedding after a shock to the body — high fever, surgery, crash dieting, severe stress | A large number of hairs enter telogen early; often temporary |
| Traction alopecia | Thinning at the hairline or parting from prolonged tension — tight braids, weaves, ponytails, extensions | The one type a cosmetologist can cause and prevent: loosen tension and rotate styles |
| Trichotillomania | Patchy loss from compulsive hair pulling | A psychological disorder; treat gently and suggest professional help |
A classic scenario question: a client who always wears tight braids shows thinning along the hairline — the answer is traction alopecia, and the professional response is to reduce tension, not to apply a chemical service over already stressed follicles.
Hair Analysis Before Services
Before any chemical service, the cosmetologist performs a structured analysis. Each test answers a practical question:
- Porosity test — take a few strands and slide fingers from end to scalp, or mist a strand and watch absorption. Rough-feeling hair or fast absorption means high porosity; smooth, resistant hair means low porosity. High-porosity hair processes chemical services faster and needs milder products and shorter timing.
- Elasticity test — stretch a wet strand. Normal wet hair stretches about 50% of its length and springs back. Hair that stretches little and snaps is brittle (often dry); hair that stretches far and stays limp or breaks easily is weak and may not tolerate a chemical service at all.
- Texture — strand diameter: coarse, medium, or fine. Fine hair processes faster and is more easily damaged; coarse hair resists and may need stronger formulas or longer processing.
- Density — hairs per square inch: thin, medium, or thick. Density guides product amount, sectioning, and cutting technique.
Putting it together in exam language: analysis results are not trivia — they are the justification for every product and timing choice. A question describing fine, highly porous hair being scheduled for a relaxer expects you to choose the gentlest option, perform a strand test, and monitor processing closely.
When to Refer to a Physician
Cosmetologists work on healthy hair and scalp. Refer out — and postpone chemical services — when you see sudden patchy loss (alopecia areata), loss accompanied by redness, scaling, or lesions, any loss following illness or medication change, or any scalp condition you cannot confidently identify. Diagnosing and treating hair loss is medical practice; the cosmetologist's role is recognition, gentle handling, and referral. Exam questions reward the response "refer to a physician" whenever a disorder looks medical rather than cosmetic.
Approximately what percentage of scalp hair is in the anagen phase at any given time, and how long does that phase typically last?
A longtime braid client shows gradual thinning and short broken hairs along the front hairline where the braids are anchored. Which type of hair loss is this, and what caused it?