What I Wish I Knew Before Laser Hair Removal

Key Takeaways

• Laser hair removal works by targeting melanin in the hair follicle using concentrated light energy.
• Treatment is most effective during the anagen (active growth) phase of the hair cycle.
• Skin type, hair colour, hormone levels, and follicle depth all influence results.
• Redness, swelling, and temporary changes in pigmentation are common side effects that typically last only a short time.
• Proper pre-treatment preparation ensures safer and more effective outcomes.
• Hair begins to shed 7 to 21 days after treatment and continues to thin over multiple sessions.
• Most individuals need 6 to 8 sessions for long-lasting reduction, with occasional maintenance.

Science Behind Laser Hair Removal

Laser hair removal works by converting light into heat to selectively damage hair follicles. The process relies on a principle called selective photothermolysis. This means the laser targets melanin, the pigment in hair while leaving the surrounding skin largely unaffected. Once the light is absorbed, the energy heats the follicle to a point where it disrupts future hair growth.

Each laser system uses a specific wavelength of light. The Alexandrite laser, for example, operates at 755 nanometres and is often used for lighter skin tones. For deeper skin tones, Nd: YAG lasers at 1064 nanometers are typically preferred. These differences matter because the depth of penetration and melanin absorption vary with each wavelength.

Key Biological Factors That Influence Treatment Outcomes

Laser removal treatment is not a one-size-fits-all procedure. While the laser system provides the energy, it is the biology of the individual that determines how well the treatment works. Several biological factors influence the effectiveness, safety, and longevity of results. 

Hair Growth Cycle

Hair grows in three distinct phases: anagen (active), catagen (transition), and telogen (resting). Only hair in the anagen phase contains a fully intact follicle with sufficient melanin to absorb laser energy effectively. 

Around 10% to 20% of hair is in this phase at any given time. This is why most treatment plans require six to eight sessions, spaced several weeks apart, to ensure that each area is targeted when the maximum number of follicles is in their active stage.

The duration of these phases varies depending on body region, age, and genetics. For example, facial hair tends to cycle more quickly than leg hair. Treatment outcomes improve when sessions are timed according to the natural growth cycle of the targeted area.

Skin Phototype and Melanin Distribution

The Fitzpatrick scale classifies skin phototypes from Type I (very light) to Type VI (very dark). Skin with lower melanin content (Types I–III) allows lasers to focus energy directly into the hair follicle with reduced risk to surrounding tissue. 

Higher phototypes (Types IV-VI) contain more melanin in the epidermis, which increases the chance of absorbing laser energy into the skin rather than the hair. This can raise the risk of burns or post-inflammatory pigmentation if not managed properly.

To address this, longer wavelengths such as 1064 nm (Nd: YAG laser) are often used for darker skin types. These wavelengths penetrate deeper into the dermis while avoiding excessive interaction with melanin in the surface layers.

Hair Color, Thickness, and Follicle Structure

Laser energy is most efficiently absorbed by coarse, dark hair due to the higher melanin content. Black or brown terminal hairs typically respond well to treatment. In contrast, lighter hair colours, such as blonde, red, or grey, contain little to no eumelanin and therefore absorb less energy. 

As a result, these hair types may show limited improvement or require alternative treatment approaches.

Hair thickness also plays a role. Thicker hairs absorb and retain heat more effectively, allowing more complete damage to the follicle. Fine or vellus hairs may not generate enough heat during treatment to disrupt the follicle, often requiring more sessions or higher energy levels.

Hormonal Influence

Hormones regulate many aspects of hair growth, particularly in areas like the face, neck, chest, and abdomen. Androgen-sensitive regions are more susceptible to hormonal imbalances. Women with polycystic ovary syndrome (PCOS) were found to have a 40% higher rate of regrowth within one year of completing laser hair removal compared to women without hormonal imbalance.

Even in individuals without diagnosed hormonal conditions, life stages such as puberty, pregnancy, or menopause can influence outcomes. In cases where hormones drive persistent growth, laser hair removal may still reduce density and slow regrowth, but results may require ongoing maintenance.

Follicle Density and Depth

Follicles vary in both number and depth depending on the treatment area. The underarms and bikini line, for instance, have fewer but coarser and deeper follicles, while the face may have a higher density of finer, more superficial hairs. Deeper follicles often require more energy or multiple passes to reach the target zone effectively.

The depth of the follicle also affects wavelength selection. Shorter wavelengths (like those used in Alexandrite lasers) are more suitable for superficial follicles, while longer wavelengths (like Nd: YAG) penetrate deeper and are more suitable for thick or embedded follicles.

What Are the Side Effects of Laser Hair Removal? 

Laser hair removal is generally considered safe when performed with the right equipment and proper technique. Still, the procedure involves thermal energy interacting with the skin, and this can sometimes lead to temporary or, in rare cases, longer-lasting effects. Most side effects are mild and short-lived, but awareness helps set accurate expectations.

Clinical data shows that up to 96% of patients report some form of discomfort immediately after treatment. These effects typically resolve within hours to a few days. However, the likelihood of side effects can increase when skin type, laser choice, or treatment settings are not properly matched.

Common side effects include:

• Redness and swelling: These are the most frequently reported effects. They are caused by inflammation around the treated follicles and usually subside within a few hours.
• Itching and sensitivity: Some individuals experience a sensation similar to mild sunburn. This is typically temporary and more common during the early sessions.
• Dryness or flaking: Treated skin can sometimes become dry or slightly rough for a short period. This is more likely in areas with dense hair or where higher energy levels were used.
• Temporary pigment changes: Post-inflammatory hyperpigmentation or hypopigmentation may occur, particularly in individuals with darker skin tones. Most cases fade gradually within a few weeks to months.
• Follicular oedema: Small, raised bumps may appear around each follicle. This is a sign that the follicle has absorbed energy and is responding to treatment.
• Rare complications: Blistering, crusting, or scarring are uncommon but may occur if the laser is misused or if post-treatment care is inadequate.

Preparing for Your First Laser Hair Removal Session

The first laser hair removal session plays an important role in shaping how the skin and follicles respond to treatment. While the device delivers targeted energy, several external factors influence how well the laser interacts with the body. Here are a few factors to consider before preparing for your first laser session. 

What to Expect During and After the Procedure

Each laser hair removal treatment requires careful calibration of energy levels, skin protection, and post-treatment support. Knowing what to expect helps clarify how and when results may appear.

Pre-Treatment Skin Assessment

Before the laser is applied, the practitioner assesses the area to ensure the skin is prepared and free from irritation. Skin type, hair colour, and follicle density are reviewed to determine the correct laser settings. Most clinics use devices such as diode, Alexandrite, or Nd: YAG lasers, which are selected based on the depth and pigment of the targeted hair.

This customisation ensures the laser targets melanin within the follicle, not in the surrounding skin. This reduces the risk of unwanted pigment changes.

What Happens During the Session

Once the area is prepared, a cooling method is applied. This may involve cryogen spray, contact cooling, or chilled gel. Cooling serves two functions: protecting the epidermis and improving patient comfort.

As the laser is activated, it emits concentrated pulses of light absorbed by melanin in the hair. This energy converts to heat and damages the follicle. The sensation varies by individual but is commonly compared to a light snap from an elastic band or a brief prick of heat.

Smaller areas, such as the upper lip or underarms, may take 5 to 15 minutes. On the other hand, legs, chest, or back can require up to 60 minutes, depending on surface area and hair density.

Immediate Reactions After Treatment

Mild erythema (redness) and follicular oedema (small, raised bumps) are common responses. These are temporary inflammatory reactions indicating that the follicle has absorbed energy. In most cases, these effects subside within a few hours, especially when cooling products are applied immediately after treatment.

Some patients report a mild burning or tingling sensation, which is more noticeable in areas with coarse or dense hair. The skin may feel warm to the touch for the rest of the day, although this sensation typically fades by the next morning.

Hair Shedding and Visible Changes

Approximately 7 to 21 days after treatment, hair in the treated area begins to shed. This is not regrowth but a sign that the follicle has entered the telogen (resting) phase and is releasing the hair shaft. Patients may notice small hairs falling out during washing or exfoliation.

Shedding becomes more noticeable after the second or third session, particularly in areas where follicles are more densely packed. Clinical research suggests that an average reduction of 10% to 40% in hair density can be expected after each session, depending on the treatment area and individual biology.

Recovery and Aftercare Between Sessions

The skin remains sensitive for several days following treatment. To support recovery, harsh topical products such as exfoliants, retinoids, acids, and alcohol-based cleansers should not be used after laser removal.

Hydrating moisturisers, barrier-repair creams, and mineral-based sunscreens are often recommended to calm the skin and protect it from environmental stress. Sun exposure should be minimised between sessions, especially for phototypes III to VI, to reduce the risk of hyperpigmentation.

You are typically advised to wait four to eight weeks between treatments, depending on the growth cycle of the targeted area. Hair on the face cycles more rapidly than on the legs or back, which can influence the timing of follow-ups.

Before You Go…

Laser hair removal offers long-term benefits, but the experience is shaped by much more than the device alone. From how the skin responds to light energy to the way hormones and hair cycles affect outcomes, each detail plays a role in the final result. 

Understanding the science behind the procedure, preparing properly, and knowing what to expect allows for more informed choices and better outcomes over time. For those exploring laser treatments or seeking answers beyond surface-level information, related articles in this series take a deeper look at the biology, technology, and personalised care that shape effective aesthetic treatments.

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2. How Long Between Laser Hair Removal Sessions?
3. Laser Hair Removal for Men
4. Is Laser Safe for Dark Skin?

About the Institute of Medical Physics 

The Institute of Medical Physics, founded by Dr. Emanuel Paleco, is a premier medical laboratory specialising in Medical and Aesthetic Laser Science. With a flagship clinic in King’s Cross and additional locations in North London and Essex, the Institute is at the forefront of laser science innovation. 

Experience advanced laser science and innovative medical treatments. Book a consultation with Dr. Emanuel Paleco and his expert team at the Institute of Medical Physics.