Study guide
Before any device fires, the technician must read the client: their skin color, hair color, medical history, and expectations. This chapter covers the Fitzpatrick scale, the hair growth cycle that dictates timing, and the screening that identifies who can be treated safely, who must wait, and who must be turned away. Careful evaluation is the single best protection against burns, pigment changes, and disappointed clients.
Fitzpatrick Skin Types and Risk
The Fitzpatrick scale classifies skin into six types based on how it responds to sun exposure, and it is the backbone of treatment planning. Type I is very fair skin that always burns and never tans; Type II is fair skin that burns easily and tans minimally; Type III is medium skin that sometimes burns and tans gradually; Type IV is olive or light brown skin that rarely burns and tans easily; Type V is brown skin that very rarely burns; and Type VI is deeply pigmented dark brown to black skin that never burns. The scale matters because it estimates how much melanin sits in the epidermis, which is exactly the pigment that can absorb laser energy at the surface and cause harm. Lower Fitzpatrick types (I through III) tolerate higher fluences and shorter wavelengths with relatively low risk because there is little competing surface melanin. Higher types (IV through VI) carry greater risk of burns and pigment changes, so they require longer wavelengths such as the 1064 nm Nd:YAG, longer pulse widths, aggressive cooling, and more conservative fluence. A technician who misjudges a client as a Type III when they are actually a Type V may deliver too much energy to the surface and cause a burn or hypopigmentation. Correctly typing every client is therefore a foundational safety step, not a formality.
The Hair Growth Cycle
Hair grows in cycles, and laser hair removal only works on hairs in the right phase, which is why multiple sessions are always required. There are three phases. Anagen is the active growth phase, when the hair is firmly attached to the follicle and packed with melanin; this is the only phase in which laser energy reliably conducts down the shaft to destroy the follicle. Catagen is a brief transitional phase, when the follicle begins to shrink and detach. Telogen is the resting or shedding phase, when the hair is loosely held and largely disconnected from the base, making treatment ineffective. At any given moment only a fraction of the hairs on a body area are in anagen, and different body regions cycle at different rates. Because the laser can only destroy follicles caught in anagen, a single session treats only the currently active hairs, and repeated sessions spaced weeks apart are needed to catch other hairs as they enter their growth phase. Understanding this cycle explains both why a course of treatment is required and why realistic timing expectations must be set with every client. It also explains why treatment intervals are keyed to how fast a particular area cycles, a point developed further in the treatment planning chapter.
History, Screening, and Contraindications
A thorough intake protects the client and the technician. Screening covers medical history, medications, skin conditions, prior treatments, and recent sun exposure. Several contraindications must be identified before treatment. A recent tan, whether from the sun or a tanning bed, temporarily raises epidermal melanin and sharply increases burn and pigment-change risk, so treatment is typically postponed until the tan fades. Pregnancy is commonly treated as a reason to defer, since hormonal changes affect hair growth and safety data is limited; most technicians wait until after pregnancy. A history of keloid or hypertrophic scarring signals that the skin may heal abnormally and warrants extra caution or referral. Active infections, open lesions, cold sores, or inflamed skin in the treatment area must clear before treatment. Certain conditions and a personal or family history of skin cancer in the area may require physician clearance. The screening also asks about photosensitizing medications and conditions, discussed next. A useful habit is to document everything: a client named James who reports a beach vacation two days ago should have that noted and his session rescheduled, protecting both his skin and the technician's record. Screening is not a one-time event; it should be repeated at each visit because medications, sun exposure, and skin status change over time.
Photosensitizers, Color Matching, and Expectations
Some medications and conditions make skin abnormally reactive to light, a state called photosensitivity, which raises the risk of burns and pigment changes. Common photosensitizing agents include certain antibiotics such as tetracyclines, some acne medications including isotretinoin (often requiring a waiting period after stopping), certain diuretics, St. John's Wort, and topical retinoids. Recent chemical peels or herb-and-drug combinations a client may not think to mention all belong on the intake form. Beyond medications, the technician must match skin and hair color to predict results. Laser hair removal works best when there is high contrast between light skin and dark, coarse hair, because melanin-rich dark hair absorbs the light while light skin does not compete for it. It works poorly on light-colored hair, white, gray, red, or very blond, because those hairs contain little melanin for the laser to target, regardless of the device. This limitation must be explained honestly. Setting realistic outcome expectations is an ethical duty: laser hair removal produces long-term reduction, not guaranteed permanent removal of every hair, results vary by individual, hormones can drive regrowth, and maintenance sessions are often needed. A technician who promises total permanent removal misleads the client and invites complaints. Clear, honest expectation-setting is both good practice and, as later chapters show, part of professional ethics and consent.
Key terms
- Fitzpatrick scale
- — A six-type classification of skin based on how it responds to sun exposure, used to estimate melanin and treatment risk.
- Fitzpatrick Type I
- — Very fair skin that always burns and never tans; lowest surface melanin and generally lowest treatment risk.
- Fitzpatrick Type VI
- — Deeply pigmented dark brown to black skin that never burns; highest surface melanin and greatest need for longer wavelengths and cooling.
- Anagen
- — The active growth phase of hair, when the follicle is melanin-rich and firmly attached; the only phase in which laser treatment is effective.
- Catagen
- — The brief transitional phase when the follicle begins to shrink and detach from the hair.
- Telogen
- — The resting or shedding phase when the hair is loosely held and largely disconnected, making treatment ineffective.
- Contraindication
- — A condition or factor that makes treatment unsafe or inadvisable, such as a recent tan, pregnancy, or active infection.
- Keloid
- — A raised, overgrown scar indicating abnormal healing; a history of keloids warrants caution or referral.
- Photosensitivity
- — An abnormally strong skin reaction to light, often caused by certain medications, raising the risk of burns and pigment changes.
- Photosensitizing medication
- — A drug that increases skin's light sensitivity, such as certain antibiotics, isotretinoin, or topical retinoids.
- Skin and hair color matching
- — Assessing contrast between skin and hair; treatment works best on light skin with dark, coarse hair and poorly on light hair.
- Test spot (patch test)
- — A small trial treatment on a limited area to observe the skin's reaction before treating the full region.
- Long-term hair reduction
- — The realistic outcome of laser treatment: substantial lasting reduction rather than guaranteed permanent removal of every hair.
Exam tips
- Memorize the Fitzpatrick scale end to end (I burns/never tans through VI never burns); higher types need longer wavelengths, longer pulses, and cooling.
- Only anagen (active growth) hairs respond to the laser, which is why multiple spaced sessions are always required.
- A recent tan is a temporary contraindication: it raises surface melanin and burn risk, so postpone treatment until it fades.
- High contrast wins: light skin with dark coarse hair treats best; white, gray, red, and blond hair respond poorly because they lack melanin.
- Never promise permanent removal; the correct language is long-term reduction, and screening should be repeated at every visit.