Laser Hair Removal: How It Works and What to Expect

Laser hair removal works on the principle of selective photothermolysis, using a wavelength of light that is selectively absorbed by a specific target (in this case, the melanin pigment in the hair follicle) while leaving surrounding tissue relatively unaffected. The laser energy is absorbed by melanin and converted to heat. That heat damages the follicle's structure and its ability to regrow hair, without significant damage to the surrounding skin.

Different laser wavelengths are used depending on the patient's skin tone and hair colour. The Alexandrite laser (755nm) and Diode laser (810nm) are effective for lighter to medium skin tones. The Nd:YAG laser (1064nm) penetrates deeper and has a lower affinity for melanin in the epidermis, making it the standard choice for patients with darker skin tones, where the risk of unwanted pigmentation change is higher.

Hair grows in cycles: anagen (active growth), catagen (transition), and telogen (resting). Laser treatment is only effective during the anagen phase, when the hair shaft is fully formed and connected to the follicle where the melanin target is concentrated. At any given time, only around 20–30% of hairs in a given area are in anagen, which means a single session can only treat a fraction of the follicles present.

A full course of six to eight sessions, spaced four to eight weeks apart depending on the body area, ensures that all follicles pass through the anagen phase and receive treatment. Sessions on the face may be spaced every four weeks; legs and body areas with slower hair cycles are usually treated every six to eight weeks.

The most significant factor in how well laser hair removal works is the contrast between hair colour and skin colour. The ideal scenario for laser is dark hair on fair skin, where melanin in the hair absorbs the laser energy selectively and the surrounding skin is not competing for that absorption. Patients with very light, grey, or red hair have low melanin in the hair shaft and respond poorly to laser treatment, as there is insufficient target for the energy.

Hormonal factors also influence results. Conditions such as polycystic ovary syndrome (PCOS) can stimulate ongoing hair growth despite effective laser treatment of existing follicles. In these cases, maintenance sessions may be required more frequently than average.

Sun exposure before and after treatment is an important practical consideration: tanned skin has elevated melanin levels in the epidermis, which increases the risk of post-treatment pigmentation changes. Avoiding sun exposure and applying high-factor SPF consistently throughout a course of treatment is essential.

Most patients describe the sensation of laser hair removal as a warm flicking or stinging feeling, tolerable for most, though this varies with the area being treated. The upper lip and bikini area tend to be more sensitive than the legs or underarms. Cooling systems built into modern laser handpieces significantly reduce discomfort.

After each session, the treated area may appear slightly red or feel warm for a few hours. Over the following one to three weeks, the treated hairs shed gradually as the damaged follicles release them. Between sessions, shaving is fine; waxing or threading should be avoided, as these remove the hair shaft from the follicle and reduce the available target for subsequent laser sessions.