How hair follicles respond to laser treatment varies considerably from patient to patient, between different parts of the body and from one treatment session to the next for the same person. This makes it hard to predict results.
Follicles have a great ability to self repair and regenerate. Scientists still don’t fully understand whether the whole follicular epithelium is essential to the hair growth process. Given this uncertainty, laser hair-removal systems irradiate as much of the follicle as possible. Only lasers emitting energy with wavelengths from 630 to 1100nm are capable of irradiating the entire length of hair follicles; these usually extend 2 to 5mm into the dermis. Areas of thinner skin (e.g. underarms) respond better to laser treatment than those with thicker skin (e.g. chin). Where the skin is very thick, the laser may struggle more to penetrate deeply enough into the hair follicle to destroy it entirely and prevent re-growth.
Ideal candidates for laser hair removal are people with pale skin tones and dark, coarse hair. They have a relatively high concentration of melanin in their hair follicles compared to their skin. This ensures the laser’s energy can be targeted to destroy their follicles. Patients with dark skins however, are likely to absorb energy into their epidermis, increasing the risk they suffer adverse effects from laser hair removal. Many practitioners are therefore reluctant to treat them, despite the fact that their hair tends to be darker, thicker and more obvious.
The longer-pulse Nd:YAG has been particularly popular because it has a widely acknowledged high safety record and the ability to produce:
- permanent laser hair removal for African skin
- permanent laser hair removal for Asian skin
- permanent laser hair removal for Middle Eastern skin
- permanent laser hair removal for olive skin
The Nd:YAG has achieved this safety record principally because the wavelength at which it transmits energy approximates to the target hair follicle’s thermal relaxation time. This permits safe application of higher energies to patients with darker skin tones. The Nd:YAG laser can penetrate from 5 to 7mm into the dermis, sufficient to reach the base of the hair bulb and destroy it, without disrupting the melanin in the epidermis. There is therefore a greatly reduced risk of crusting, vesiculation, dyspigmentation and other adverse epidermal effects with 1064-nm Nd:YAG laser irradiation.