How Laser Hair Removal Works

Laser hair removal works by sending light into the skin that is absorbed by the pigment in the hair. The light turns into heat, travels down the hair shaft and damages the follicle that produces it, which slows or stops future growth. Because only actively growing hairs respond well, it takes a series of sessions, and the realistic outcome is a lasting reduction in hair rather than total, permanent removal.

The principle behind it: selective photothermolysis

The scientific term for this is selective photothermolysis. Broken down, it means using light (photo) to create heat (thermo) that destroys (lysis) a chosen target while sparing the tissue around it.

Three things have to line up for this to work:

1. The right wavelength, so the light is absorbed by the target more than by the surrounding skin.
2. The right pulse length, long enough to heat the follicle but short enough that the heat does not spread too far into nearby skin.
3. The right energy, enough to damage the follicle without burning the surface.

Cooling the skin before, during or after each pulse also helps protect the surface while the deeper follicle is heated.

Melanin: the target

In hair removal, the target is melanin, the pigment that gives hair its colour. Dark hair contains a lot of melanin and absorbs laser energy well. That is why the ideal situation, from a physics point of view, has always been dark hair on lighter skin: the hair soaks up the energy while the skin absorbs relatively little.

The challenge is that skin also contains melanin. In people with medium to dark skin, or anyone with a tan, the skin competes with the hair for the light. Longer wavelengths such as Nd:YAG at 1064 nm are absorbed less by the surface pigment and reach deeper, which allows hair removal to be done more safely on darker skin. Our article on laser hair removal for different skin tones explains this further.

Hair with little or no melanin, such as blond, grey, white and many red hairs, does not absorb enough energy. Laser is generally not effective for these hair colours, and it is better to know that before starting.

Why the growth cycle matters

Each hair follicle goes through its own cycle, and at any moment the hairs in an area are at different stages:

• Anagen (growth phase): the hair is attached to the base of the follicle, where the cells that produce new hair live. This is when laser treatment is most effective.
• Catagen (transition phase): the hair detaches and the follicle begins to shrink.
• Telogen (resting phase): the old hair sits loosely before shedding, and a new hair has not yet started.

Only a portion of hairs are in the growth phase at a given session. Treatments are therefore spaced weeks apart to catch new groups of follicles as they enter anagen. The spacing differs by body area because hair cycles run faster on the face than on the legs or back. For practical numbers, see how many sessions you may need.

Reduction, not removal

Regulators and medical sources commonly describe laser treatment as producing permanent hair reduction. That means a significant, long-lasting decrease in the number of hairs that regrow after a full course. It does not mean every hair is gone forever.

After treatment, many people find that remaining hairs are finer, lighter and slower to grow. Some follicles are damaged rather than destroyed and may recover over time. Hormonal changes, such as those around pregnancy, menopause or conditions like polycystic ovary syndrome, can also stimulate new growth. Occasional maintenance sessions are common.

Results vary from person to person. Hair colour, thickness, skin tone, hormones and the body area all influence the outcome.

What happens during a session

The area is shaved beforehand so that energy goes into the follicle rather than burning hair lying on the surface. Everyone in the room wears eye protection matched to the laser. The clinician may test a small spot first to see how your skin responds, then treats the area in a grid pattern, pulse by pulse.

Most people describe the feeling as a quick snap or a hot pinprick. Cooling makes this more tolerable. Small areas can take only a few minutes, while larger areas like the legs or back take longer.

Who should not have it, or should wait

Treatment is usually postponed or reconsidered if you:

• Are pregnant (generally deferred because safety data are limited)
• Have a tan, recent sunburn or self-tanner on the area
• Have an active infection, rash, cold sore or open skin in the area
• Take medicines that increase light sensitivity, or have used isotretinoin recently
• Have a history of keloid scarring
• Have a mole or spot in the area that has changed and has not been checked

New or rapidly increasing hair growth, especially in women, can sometimes signal a hormonal condition. In that case, it is sensible to see your family doctor first. Do not stop any prescribed medication on your own; discuss it with your prescriber.

Possible risks and side effects

Most people have redness and small raised bumps around the follicles for a few hours to a couple of days. Less commonly, treatment can cause blistering, crusting, burns or infection. Pigment changes, either darker or lighter patches, can occur and are more likely in darker or tanned skin. They usually fade over weeks to months but can occasionally last longer. Rarely, some people notice increased growth of fine hair near a treated area, called paradoxical hypertrichosis.

Frequently asked questions

Why do treated hairs seem to keep growing after a session?

Hairs damaged by the laser often push out of the skin over the following one to three weeks before falling out. This shedding can look like regrowth, but it is part of the normal response.

Does laser work on peach fuzz?

Very fine, light hair usually does not contain enough pigment to respond well, and treating it may carry a small risk of stimulating growth. It is often better left alone.

Is laser hair removal the same as IPL?

No. Intense pulsed light (IPL) uses a broad range of wavelengths rather than a single one. Both can reduce hair, but they behave differently, and the right choice depends on skin and hair type.

If you are considering laser hair removal, HealthPark Medical Aesthetics can review your skin, hair colour and medical history at a consultation and explain honestly whether treatment is likely to help.