Skin Physics Spotlight: How Does Laser Hair Reduction Work?

Lasers Selectively Target Hair

Several treatments such as waxing, shaving, and plucking are all offered for hair removal, but laser hair reduction is one of the fastest growing nonsurgical procedures for both men and women. According to the American Society for Aesthetic Plastic Surgery (ASAPS), laser hair removal was listed as the top nonsurgical procedure for people 18 and under and for people between 19 and 34 years old.

Laser hair reduction works by selectively damaging the hair while reducing damage to the surrounding skin.

Lasers are a narrow beam of light formed by a single wavelength. Laser hair reduction uses these beams of light to target the pigment in the hair known as melanin to heat and damage the hair. Common types of lasers used for hair reduction are Alexandrite, long-pulse Diode, and the long-pulse Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) having wavelengths of 755 nm, 810 nm, and 1064 nm respectively. 

As mentioned earlier, the lasers target melanin - the pigment responsible for protecting the skin from harmful radiation. Melanin is found in various parts of the body, such as the eyes, hair, and skin. During laser treatments for hair reduction, the melanin inside the hair absorbs the light energy, converts it to heat, ultimately damaging the hair itself. By heating and damaging the hair and the surrounding hair follicle, the eventual outcome is a reduction in the amount and thickness of the hair.

Efficacy of Laser Treatments

Recall that one of the functions of melanin is to absorb light energy. The laser emits a light energy of a certain wavelength specific to the melanin in the hair, so the surrounding skin will not be damaged. Darker hair has more melanin than lighter hair or white hair. Thus, the ideal patient for laser hair reduction is an individual with dark hair and light skin. White hairs and light blonde hairs have very little melanin and are not targeted well with laser hair reduction.

However, laser hair reduction is still permissible for individuals with deeper skin colors. Lasers with longer wavelengths such as the long pulse-diode and the Nd: YAG laser is best for these deeper skin colors, resulting in fewer side effects of pain and post-inflammatory hyperpigmentation.

The diode, alexandrite, and Nd: YAG lasers have the best results after 6 months with repetitive treatment. The treatment may not completely remove hair, but it does provide a safe and quick procedure that can significantly reduce hair quantity and thickness. 

Potential Side Effects of Lasers

When hair heats up with laser treatment, the heat will also diffuse to the surrounding skin, which can potentially cause collateral damage. Therefore, the laser is emitted in short pulses during the procedure. These pulses prevent the heat from spreading too far and damaging the skin.

Lasers can also target other non-hair parts of the skin that have melanin too, such as the surface of the skin. This is what can lead to burns and skin discolorations. To protect against this, many laser hair reduction devices will spray a cooling agent on the skin to protect it from overheating, while allowing the laser to successfully heat up the hair. 

Complications from the treatment are determined by various factors including skin type, body location, and patient history of sun exposure (tanned skin absorbs more laser energy than untanned skin). However, side effects are usually minor and transient. Common skin reactions are pain, transient redness, and swelling around the treated hair follicles.

Practical Tips After Using Lasers

Practitioners often advise their patients to avoid sun exposure before the operation or pretreat with hydroquinone twice daily for a month to reduce inflammatory hyperpigmentation. The latter option works best for patients with darker skin types. Continued discomfort after the procedure can be reduced by ice packs or gauze soaked in cold water. Remember that these treatments are tailored to each patient and may not work with every skin type.

At-Home Devices

At-home laser hair devices have been created to account for lower cost, convenience, and luxury of hair reduction at home. However, safety issues arise due to the lack of professional oversight. It is still unclear if these devices will serve as a suitable option for use at home.