Have you ever noticed that laser hair removal seems to work quickly on some areas of the body, while others require more patience?

The answer has a lot to do with melanin, hair thickness and the natural hair growth cycle.

Understanding how melanin affects laser hair removal helps explain why dark, coarse hair often responds particularly well, why fine or light hair can be more challenging, and why results can vary significantly from one part of the body to another.

What Is Melanin?

Melanin is the natural pigment responsible for much of the colour in our hair, skin and eyes.

When it comes to laser hair removal, melanin plays an especially important role because it acts as the primary chromophore — the target that absorbs the laser’s light energy.

In simple terms:

The laser emits light → melanin in the hair absorbs the light → the energy is converted into heat → heat damages structures within the hair follicle responsible for producing new hair.

This principle is known as selective photothermolysis.

The goal is to deliver enough energy to affect the targeted follicle while protecting the surrounding skin.

Why Does Dark Hair Usually Respond Better?

Hair containing more melanin generally provides a stronger target for laser energy.

Dark, coarse terminal hairs contain relatively high concentrations of pigment and can therefore absorb laser energy efficiently. This is one reason areas with thick, dark hair may show noticeable reduction relatively early in a treatment programme.

Fine hairs contain less pigment, giving the laser less melanin to target.

This becomes even more significant with very light hair. Blonde, red, grey and white hairs contain different amounts or types of melanin — or very little pigment at all — which can make conventional laser hair removal considerably less effective.

However, melanin concentration is only part of the story.

Why Do Some Body Areas Respond Faster Than Others?

You might expect laser hair removal to work at approximately the same speed everywhere, but hair characteristics vary considerably across the body.

Areas such as the underarms and bikini region frequently contain darker, thicker terminal hairs. These characteristics make them strong targets for laser treatment.

By comparison, areas such as the arms, thighs or certain parts of the face may contain finer or less pigmented hairs.

This means two areas treated on the same person — even using the same technology — can progress very differently.

Research also shows that anatomical location itself can influence laser hair removal outcomes. Differences in hair thickness, pigmentation, density and growth cycles all contribute to how an area responds.

The Hair Growth Cycle Matters Too

Another important factor is something we cannot see: what stage of growth each individual hair is currently in.

Hair moves through several phases:

Anagen – Active Growth

This is the phase most associated with effective laser hair removal.

During active growth, the follicle contains substantial pigment and the hair remains connected to the structures responsible for its growth. This creates favourable conditions for laser energy to affect the follicle.

Catagen – Transition

The follicle begins transitioning away from active growth. It becomes a less effective target for laser treatment.

Telogen – Resting Phase

The hair is resting and will eventually shed. Treatment during this stage is generally less effective than when the follicle is actively growing.

The important point is that not every hair is in anagen at the same time.

This is why one laser session cannot target every follicle effectively and why a properly planned series of treatments is necessary.

Different Areas Have Different Hair Cycles

Hair growth cycles are not identical across the body.

The proportion of follicles actively growing at any given moment — as well as the length of the growth and resting phases — varies depending on anatomical location.

This helps explain why treatment intervals should not simply be chosen at random.

The aim is to allow another group of follicles to enter an appropriate stage of growth before the next session.

A treatment protocol should therefore consider the treatment area, hair characteristics, skin type and previous response, rather than applying exactly the same approach to every patient.

What About Melanin in the Skin?

There is another important part of the equation.

Melanin isn’t found only in hair. It is also present in the skin.

Because laser hair removal targets melanin, the practitioner needs to create a balance between delivering energy to the pigment inside the hair and limiting unnecessary absorption by pigment in the surrounding epidermis.

This is particularly important for darker skin tones and tanned skin, where there is more epidermal melanin competing for the laser’s energy.

That doesn’t mean darker skin cannot be treated. Instead, appropriate technology, wavelength selection and treatment parameters become especially important.

Why Wavelength Matters

Different laser wavelengths interact with melanin differently and penetrate the skin to different depths.

This is one reason professional laser platforms can offer different wavelengths for different patient profiles.

For example, Candela systems such as the GentleMax Pro® and GentleMax Pro Plus® combine two established wavelengths:

755 nm Alexandrite

Alexandrite technology has a strong affinity for melanin, making it particularly effective for appropriately selected patients with pigmented hair.

1064 nm Nd:YAG

The longer 1064 nm wavelength is absorbed less strongly by epidermal melanin and penetrates more deeply, which can make it suitable for treating a broader range of skin types, including darker skin tones when used appropriately.

Having access to both wavelengths gives trained practitioners greater flexibility when selecting treatment parameters according to the patient’s skin type, hair characteristics and treatment area.

Why the Same Patient Can Have Different Results

Imagine a patient treating several areas simultaneously.

Their underarms may have thick, dark hairs with plenty of melanin. Their thighs may have finer hairs with less pigment, while facial hair may be influenced by different growth patterns or hormonal factors.

Even though all three areas belong to the same person, they are three very different laser targets.

This is why comparing session numbers between different body areas — or even between different patients — can be misleading.

Laser hair removal isn’t simply about counting treatments. Results depend on a combination of:

• Hair colour and melanin concentration
• Hair thickness and density
• Skin type and pigmentation
• Hair growth stage
• Anatomical treatment area
• Hormonal influences
• Laser wavelength
• Fluence, pulse duration and spot size
• Treatment intervals
• Practitioner assessment and technique

Why Professional Assessment Matters

Modern laser technology provides practitioners with considerable flexibility, but technology alone does not determine treatment success.

Understanding the relationship between melanin, wavelength, skin type and hair biology is essential when developing an appropriate treatment protocol.

Practitioners should evaluate how the hair responds between sessions and adjust treatment parameters and intervals when appropriate rather than treating every area according to an identical formula.

This is also why professional-grade laser systems with multiple treatment options can be valuable in clinical practice.

The Bottom Line

Melanin is at the centre of laser hair removal.

It provides the target that allows laser energy to reach the hair follicle, which is why dark, coarse hairs generally respond more effectively than fine or lightly pigmented hairs.

But melanin isn’t the only factor determining results.

Hair growth cycles, anatomical location, skin pigmentation, hair thickness, hormonal influences and treatment parameters all contribute to how quickly an area responds.

So, if one area appears almost hair-free while another still needs several sessions, it doesn’t necessarily mean the treatment isn’t working.

It may simply be the biology of the hair.

At Crystal Medical, we supply advanced Candela laser technologies to aesthetic and medical professionals across Cyprus, helping clinics access versatile systems designed to address different skin types, hair characteristics and treatment needs.

For more information about available Candela laser systems and professional solutions, contact the Crystal Medical team.