Laser Hair Removal
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Direct answer
Melanin in the hair shaft and bulb is the target chromophore, which is why laser hair removal works brilliantly on dark hair in fair skin and disappoints on white, grey and red hair. The governing principle is selective photothermolysis — Anderson and Parrish's 1983 concept: pick a wavelength melanin absorbs, deliver it in a pulse shorter than the follicle's thermal relaxation time (tens of milliseconds), and spare surrounding skin with matched fluence and cooling. Device choice follows Fitzpatrick type: ruby 694 nm for I-II, alexandrite 755 nm for I-III, diode 800-810 nm across I-IV, and long-pulsed Nd:YAG 1064 nm — deep-penetrating and melanin-sparing — the standard for Indian type IV-VI skin. Anagen follicles are selectively vulnerable, so sessions repeat every four to eight weeks across six to eight sittings, shaving (never waxing) between visits.
What you must remember
- Selective photothermolysis triad: wavelength preferentially absorbed by chromophore, pulse duration no longer than the target's thermal relaxation time, and fluence sufficient for destruction without collateral damage — plus surface cooling as the practical fourth.
- Wavelength-Fitzpatrick matching: ruby 694 nm (most melanin-absorbed, safest in very fair skin only), alexandrite 755 nm (efficient, types I-III), diode 800-810 nm (the global workhorse, types I-IV), long-pulsed Nd:YAG 1064 nm (deepest, least epidermal melanin absorption — the standard for Indian skin).
- Hair-cycle logic and honest expectations: melanogenesis and mitosis live in anagen while telogen follicles escape — hence six to eight sessions at 4-8 week intervals; the endpoint is reduction, not eradication, maintenance is yearly, and white and grey hairs are immune for lack of melanin (electrolysis answers those).
- Preparation rules: shave the day before (long hair above skin wastes and scatters energy); no waxing, plucking, threading or bleaching for four to six weeks prior — those remove the target; no recent tanning or active infection.
- Contraindications and ocular safety: recent isotretinoin (conventional six-month wait), photosensitising drugs, active infection, pregnancy (relative) and keloidal tendency; the retina absorbs these wavelengths, so eyewear is mandatory for patient and operator, intraocular shields for periorbital work.
- Complication cluster: burns and blistering from fluence errors, post-inflammatory hyperpigmentation (the commonest Indian complaint), hypopigmentation, folliculitis, and paradoxical hypertrichosis — fine facial hair coarsening on darker-skinned women, documented with low fluences and PCOS backgrounds.
- Indian endocrine note: jaw-and-chin hirsutism in women deserves a PCOS workup before cosmetic lasering, because the androgen drive defeats the machine.
Choosing the machine for the patient in front of you
A 27-year-old woman, Fitzpatrick type V, wants her facial hair gone; the growth sits on jaw and chin, coarse and dark. Step one is endocrine triage — irregular cycles and acne prompt a PCOS screen before any laser, since untreated hormones blunt the yield. Step two is device selection: her melanin-rich epidermis competes for every photon, so the long-pulsed Nd:YAG 1064 nm with contact cooling is chosen; an alexandrite handpiece would trade speed for burn risk. Step three is parameter discipline: conservative test spots, forty-eight hours of observation, then the working fluence with integrated cooling. Step four is the calendar: six-week facial intervals, longer on the body, shaving permitted and waxing forbidden between visits. By session six her coarse hair is substantially reduced, the vellus fringe honestly unresponsive, and the plan shifts to twice-yearly maintenance plus gynaecology co-management of the PCOS — a whole answer, not just a fluence.
Where candidates slip
The first slip is wavelength amnesia: pairing alexandrite with type VI skin or claiming ruby suits everyone flips the safety logic — the deeper the wavelength, the safer the dark skin — and Nd:YAG 1064 nm is the exam's answer for Indian patients. The second is mechanism shorthand: "laser kills the follicle" earns nothing; the marks sit in selective photothermolysis's three parameters, especially pulse duration matched to thermal relaxation time. Third, the paradox: candidates call paradoxical hypertrichosis mythical when it is documented, classic on the faces of darker-skinned women at low fluences. Fourth, the timing errors — waxing before sessions or lasering tanned, isotretinoin-exposed or infected skin — each a planted trap; and finally grey-white hair immunity: no melanin, no target, the sentence the exam wants verbatim.
Frequently asked questions
Which laser is preferred for Fitzpatrick type IV-VI Indian skin?
Long-pulsed Nd:YAG 1064 nm, whose deeply penetrating, melanin-sparing wavelength minimises epidermal injury.
What is selective photothermolysis?
Matching wavelength, pulse duration shorter than the target's thermal relaxation time, and fluence so energy localises in the chromophore — follicular melanin here — sparing surrounding tissue.
Why must hair not be waxed or plucked between sessions?
Those methods remove the pigmented shaft and bulb the laser targets; only shaving preserves the target while keeping surface hair short.
What is paradoxical hypertrichosis after laser hair removal?
Coarsening and densification of fine hair, typically on the face of darker-skinned women, classically associated with low fluences and underlying hormonal factors.
Why are white and grey hairs unresponsive to laser hair removal?
Their follicles lack melanin, the absorbing chromophore, so the laser energy has no target — electrolysis or other mechanical methods are needed.