Medical hair removal (laser): How much do hairs reduce? What long-term research shows about effectiveness and limits

Studies tracking medical hair removal lasers over periods longer than the hair growth cycle report that hair is reduced by approximately 30–84%[1]. Effectiveness increases with repeated treatments, but complete hair elimination is rare[2]. The degree of reduction varies by body area, device type, skin tone, and hair texture[1][3].

How much does hair reduce with medical hair removal?

A summary of 5 long-term randomized controlled trials (studies where treatment assignment was determined by random draw) involving 223 people found the following.[1]Hair reduction rates were 35–84.25% with alexandrite laser, 30–73.61% with Nd:YAG laser, and 32.5–69.2% with diode laser.[1].

A summary of 11 other trials involving 444 people also showed approximately 50% reduction up to 6 months with alexandrite and diode lasers.[2]Effectiveness increases with repeated treatments, but complete hair elimination is rare.[2].

Does effectiveness differ by body area?

Hair reduction rates vary by body area. Across all devices, legs showed the greatest reduction and face showed the least.[1].

Hair growth cycles occur approximately every 1 year on the legs and every 6 months on the face.[1]Since facial hair tends to be harder to reduce than leg hair, confirming the expected number of treatments in advance will minimize discrepancies with expectations.

Does the device type change results?

Which device is most effective is not clear. A review comparing 4 types of lasers did not find clear differences in hair reduction.[2].

Studies comparing diode and Nd:YAG lasers show mixed results: some report a difference (diode 78.6%, Nd:YAG 64.5%), while others report no difference.[3].

A study of 60 people using 3 types of lasers sequentially showed 75.07% hair reduction 6 months after the final treatment.[4]A study of 10 people applying 2 types of lasers simultaneously to underarm hair showed 70.12% reduction on the side receiving both, 46.70% with alexandrite alone, and 27.74% with Nd:YAG alone.[5]Both studies involved small sample sizes, so treat the results as one reference point.

Does skin tone or pain affect device selection?

For people with darker skin tones, device selection becomes especially important. Longer-wavelength diode and Nd:YAG lasers are reported to be less affected by skin tone and cause less pain and post-inflammatory hyperpigmentation (brown discoloration remaining on skin).[3].

The Japanese Society for Aesthetic Plastic Surgery guidelines strongly recommend Nd:YAG laser as effective for hair removal regardless of skin tone.[6]Diode laser was developed for darker skin and has nearly 25 years of established use.[7]Alexandrite laser causes less pain and produces effective results, but effectiveness may vary by hair and skin tone, and paradoxical hair growth ('terminal hair growth') can occur; caution is advised.[8].

Pain differs by device. On a 4-point pain scale, Nd:YAG scored 3.5, diode 2.0, and alexandrite 2.3.[4]In Asian skin, diode laser has been reported to cause less pain than Nd:YAG.[3].

What side effects can occur?

The most common are redness at the treated site and swelling around hair follicles. In a 60-person study, both resolved within a few days, and no participants had scarring or long-lasting color changes.[4].

When treating around the face, eye protection is essential. Laser light entering the eye can cause retinal burns and other effects on vision.[3]People with hormonal conditions or menstrual irregularities are advised to first rule out underlying disease causing increased hair growth.[3].

What should I confirm before treatment?

During consultation, ask the following:

Body area: What degree of reduction is expected for the area you wish to have treated?[1]

Device: Which device is suited to your skin tone and hair texture?[3][6][7]

Pain: Are there measures such as cooling available if pain is severe?[4]

Terminal hair growth: Which areas may be affected and what is the plan if it occurs?[8]

How much your hair will reduce and how many treatments are needed cannot be determined from an article alone. At your appointment, tell your doctor your skin tone, sun exposure history, and any medical conditions, and confirm the recommended device and number of treatments for each area.