How many sessions of medical laser hair removal are needed, and how much hair reduction can you expect? Types of lasers and differences from salon hair removal

Medical laser hair removal works by having the laser light absorbed by the black pigment (melanin) in hair, converting it to heat, and destroying the tissue that produces hair to reduce hair growth.[1]With repeated sessions, hair gradually decreases, but one session is not enough, and it is rare for all hair to disappear completely.[2]Effectiveness varies depending on hair color, root depth, and skin tone.[3].

Why does hair decrease?

Laser light is absorbed by melanin in the hair and becomes intense heat. This heat damages the base of the hair root and the stem cells that continuously produce hair, making it harder for hair to grow.[1].

The three main types of lasers used for hair removal are alexandrite (755 nm), diode (808–810 nm), and Nd:YAG (1064 nm).[1]Gentlelase Pro is an alexandrite laser device among these.

The Japanese Society for Aesthetic Surgery guidelines "strongly recommend" long-pulse alexandrite laser because, when the skin is cooled during treatment, it protects the epidermis, causes less pain, and provides long-lasting hair removal effects.[3].

How many sessions and how much reduction?

As a guideline, approximately half the hair is reduced after several sessions, and about 70–80% after six months following completion of the course. In a study where 50 people with excessive facial hair received 3 treatments at 5-week intervals, hair reduction one month later was 56%.[4].

In a compilation of over 2000 patients treated with alexandrite laser, average hair reduction six months after the final treatment was approximately 80%.[2]Long-term effectiveness is reported in the range of 65–80.6%.[5].

Effectiveness increases with repeated sessions, but it is rare for hair to disappear completely.[2]Each treatment provides a 2–6 month effect of "delayed hair growth," and treated hair may regrow years later.[5]Hair that regrows is typically finer and lighter in color.[5].

In a study of 60 people using three types of lasers sequentially, hair reduction at six months averaged 75.07% across the body.[1]Hair does not fall out immediately after treatment but sheds over days to weeks.[5].

Does effectiveness vary by skin color or hair color?

Yes, it does. The guidelines state that hair root depth, hair color, and skin color produce differences in effectiveness.[3]Because laser targets melanin in hair, if skin melanin is abundant, light is also absorbed there, increasing the risk of burns and color changes.[5].

For people with darker skin, the Nd:YAG laser, which can be used regardless of skin tone, is "strongly recommended."[6]In a study comparing underarms of 30 dark-skinned women, both the method of repeated low-power alexandrite treatments and the high-power Nd:YAG method reduced hair, with the alexandrite group showing greater reduction.[7].

Treatment cannot be performed on sunburned skin, so UV protection before treatment is essential.[5].

What are the side effects? What is hypertrichosis?

The most common is pain and discomfort during treatment.[8]Bruising (red-purple discoloration), blistering, and scab formation may also occur and are managed with topical medications.[8]Pigmentation changes are usually temporary and fade over time.[8].

Redness and puffiness around hair follicles typically subside within days.[1]In darker-skinned people, note that pigmentation and depigmentation occur more easily.[9].

Hypertrichosis is a phenomenon where fine hair in the treated area becomes thicker and darker. The guidelines mention this possibility with alexandrite.[3]Conversely, a study of 60 people using three combined lasers reported no cases of hypertrichosis.[1]Whether it occurs cannot be predicted in advance, so in areas with fine hair, changes after treatment are monitored together.

How is it different from salon IPL hair removal?

The difference is the type of light. Medical laser uses a single wavelength focused on hair melanin. IPL (intense pulsed light) uses light containing a broad range of wavelengths (500–1200 nm), allowing large areas to be treated quickly in one session.[10].

The Japanese Society for Aesthetic Surgery guidelines "weakly recommend" IPL because, although it lacks the selectivity for melanin of single-wavelength lasers, it has a large treatment area and causes less pain.[11]There is a difference from the "strong recommendation" for alexandrite and Nd:YAG.[3][6].

In IPL comparative trials, 4–8 sessions report 60–75% hair reduction, but complete clearance is uncommon, and regrowth increases after six months.[10]In a study comparing hair reduction after 3 treatments, alexandrite achieved 53%, IPL 50%, and Nd:YAG 39%, with all decreasing by six months.[1].

What should the examination confirm to determine the right treatment for you?

The examination should confirm skin tone and sun exposure history, hair thickness and color, the area to be treated, medications you are taking, and whether the area has fine hair prone to hypertrichosis. This determines device selection and power settings.

Ask in advance about the number and interval of sessions, pain management, and contact information for redness or pigmentation changes. Because reduction varies with the combination of hair and skin characteristics, it is best to confirm your individual outlook with your doctor during the examination.