Pulsed light hair removal: what are the risks?

Theintense pulsed light hair removalis a method based onphotothermolysis, that isaimed at generating specific thermal damage to hairs while minimising damage to surrounding tissues. The device emits pulses of light that are captured by melanin, a pigment present in hairs and responsible for their colour. It acts as a chromophore, absorbing light at a specific wavelength. It then transfers this energy to surrounding molecules, causing a temperature increase. This heat is then transmitted to the hair bulb, resulting in significant damage, includingapoptosis (programmed cell death) of the hair follicle.

Although it is reputed to be painless, hair removal using pulsed light can nevertheless cause a sensation of tingling and warmth. Indeed, the device emits light rays that produce heat upon contact with the skin's melanin. This heat is then used to destroy the hair roots. Although unpleasant, the pain is nonetheless bearable. In some cases, it can cause transient burning sensations, primarily in individuals with fair skin due to a low melanin content.

Beyond minor effects, pulsed light hair removal is responsible for thermal effects, including transient erythema. This is characterised by redness in the treated area due to dilation of the superficial skin vessels under the influence of the rays. This effect is quite common and was encountered in 92% of individuals who underwent pulsed light hair removal in a clinical study.

This phenomenon is typically accompanied by a perifollicular oedema observed in 72% of cases and by desquamation. Furthermore, a purpura can be induced by pulsed light hair removal. Unlike erythema, it appears as purple or violet spots that do not fade under pressure.

Pulsed light hair removal can lead to the formation of bulbs, vesicles, and crusts, resulting from skin irritation. Although the Fox-Fordyce disease is rare, it has been observed in a subject at the axillary level after a session of pulsed light hair removal. It presents itself through pruritic follicular papules, although there are no clear explanations for its occurrence following a hair removal session.

This process can stimulate hair growth and cause the emergence of new hairs in the treated area. In some instances, the heat destroys the melanin present in the skin, which results in causing pigmentation disorders, either hyperpigmentation or hypopigmentation.

Pulsed light hair removal can also pose serious risks to certain individuals. These are characterised by chronic neuropathic pain when the light rays reach the nervous system. Moreover, some severe effects such as eye injuries have been reported following improper handling of the laser that was directed towards the eye, damaging the retina, cornea, or iris.

It should be noted that risks can be heightened by certain factors such as medication intake or the individual's skin type. This technique is incompatible with photosensitising medications which can pose risks, such as burns, depigmentation or an increased sensitivity to light in general.

It is not recommended for pregnant and breastfeeding women who, during this period, have a high production of hormones that can lead to the appearance ofpigmentation spots,such as apregnancy mask. These are due to a high production of melanin which can absorb pulsed light and cause burns.

For those not undergoing any specific treatment, risks can be minimised by avoiding the application of any skincare products on the waxed area that could alter skin sensitivity. Exposure to natural or artificial UV rays should also be avoided after each session, as the skin is more sensitive and there is a higher risk of burns. Moles are the result of an excess of melanin and should be given special attention during the session to avoid burns. It is therefore advised to protect them by covering with a white pencil or a plaster.

• WEISS R. A. & co. Hair removal with a non-coherent filtered flashlamp intense pulsed light source. Lasers in Surgery and Medicine (1999).

• Risks associated with intense pulsed light epilators. Opinion of Anses Collective Expertise Report (2021).