Why Heat is the Worst Enemy for Melasma and Why Lasers Don't Always Have the Same Effect

By Gay Wardle

Melasma is one of the most stubborn and emotionally challenging pigment conditions to manage. Unlike a sunspot or freckle that can often be lightened quickly with targeted treatment, melasma has a far more complex nature. It’s not just “pigment in the skin” — it’s a disorder driven by a web of internal and external factors, including hormonal influence, genetic predisposition, inflammation, and environmental triggers.

It is also a chronic condition, meaning that even when the surface pigment fades, the underlying susceptibility remains. This makes it incredibly easy to flare up and notoriously difficult to keep under control. For practitioners, the key to successful melasma management lies in understanding what fuels it — and one of the strongest triggers is heat.

The Underlying Nature of Melasma

Melasma presents as irregular, often symmetrical patches of brown to grey-brown pigmentation, most commonly on the cheeks, forehead, upper lip, and jawline. Its pigment can be located in the epidermis, dermis, or both. The exact cause is still not fully understood, but research consistently shows that melanocytes in melasma behave differently from those in unaffected skin.

They are:

• Larger in size

• Contain more dendrites (extensions used to transfer pigment to surrounding keratinocytes)

• More sensitive to stimulation — whether from UV, visible light, hormones, inflammation, or heat

This heightened reactivity means that triggers which may cause only minimal pigmentation in non-melasma skin can produce significant, rapid pigment changes in melasma-prone skin.

How Heat Activates Melanogenesis

When skin tissue heats up, a chain of biological events occurs that is remarkably similar to the skin’s UV defence response.

1. Tissue Temperature Rise

Heat from the environment (hot weather, saunas, hot yoga), from mechanical friction (vigorous scrubbing, dermabrasion), or from treatments (IPL, RF, aggressive lasers) can increase the temperature of the skin’s basal layer to around 40–42°C or more.

2. Vasodilation and Increased Blood Flow

The body responds to this heat by dilating blood vessels, allowing more blood, oxygen, and nutrients into the tissue. While this is a normal cooling and healing mechanism, it also brings inflammatory cells to the site.

3. Release of Inflammatory Mediators

Inflammatory chemicals such as prostaglandins, leukotrienes, and cytokines flood into the area. These are “messenger molecules” that signal the skin to protect itself.

4. Hormonal Signalling

Keratinocytes release alpha-melanocyte-stimulating hormone (α-MSH). This hormone binds to melanocortin 1 receptors (MC1R) on melanocytes, switching on tyrosinase — the key enzyme responsible for the production of melanin.

5. Pigment Production and Transfer

Tyrosinase begins converting the amino acid tyrosine into melanin. Melanocytes package this melanin into melanosomes and transfer it through their dendrites to surrounding keratinocytes, where it becomes visible as pigmentation.

Why This is a Problem for Melasma-Prone Skin

In healthy, non-melasma skin, this melanin production slows down once the trigger is removed. But in melasma:

• Melanocytes are already primed to overproduce pigment.

• They react more quickly and more aggressively to even mild heat.

• The pigment-making process continues for longer.

• Pigment is distributed more diffusely, often leading to a broader and deeper pigmentation pattern than before the trigger.

This is why something as seemingly harmless as a facial steam, hot shower, or a walk in hot weather can set melasma back weeks or months.

Why IPL is the Worst Choice for Melasma

Intense Pulsed Light (IPL) is widely used to treat pigmentation, vascular conditions, and photoaging. However, its design makes it one of the riskiest devices for melasma.

Here’s why:

• Broad-spectrum light: IPL delivers multiple wavelengths in each pulse, targeting all melanin in the skin — not just the unwanted pigment.

• Bulk heating: The light energy is converted to heat within the skin, and because it’s non-specific, this heating is widespread.

• Superficial improvement, deeper damage: While surface pigment may initially lighten (giving a false sense of success), the bulk heating has already activated melanogenesis deep in the skin, setting the stage for rebound pigmentation.

The result? Within weeks to months, pigmentation often returns darker, more diffuse, and more resistant to treatment than before. In some cases, it spreads into areas that were previously unaffected.

The Typical Sequence of IPL on Melasma

1. Initial Lightening

The treated pigment oxidises and flakes off, giving the client visible improvement in the first 1–2 weeks.

2. Invisible Trigger

Deep in the skin, melanocytes have been stimulated by the treatment heat, and the pigment-making process is underway.

3. Rebound Pigmentation

Within 4–12 weeks, new pigment surfaces. It may be darker and cover a larger area than the original melasma.

4. Increased Sensitisation

The melanocytes become even more reactive, making future treatment more challenging.

Why Lasers Don’t Always Produce the Same Outcome

While lasers also use light energy, they differ fundamentally from IPL in that they emit a single, specific wavelength of light. This wavelength can be selected to target a specific chromophore at a defined depth with much greater precision.

In melasma, certain lasers — particularly low-fluence Q-switched and picosecond lasers — can be used to break down pigment particles with minimal heat damage to surrounding tissues. This approach is sometimes called “laser toning.”

However:

• Not all lasers are safe for melasma.

• Incorrect settings or excessive energy can still create enough heat to trigger rebound pigmentation.

• Even with the right technology, treatment should be conservative, slow, and always paired with pigment-suppressing skincare.

The main difference is that a carefully chosen laser, in experienced hands, can reduce pigment without the same degree of bulk heating that makes IPL so risky.

Breaking the Heat–Pigment Cycle

The safest and most effective approach to melasma is built on prevention and control, rather than aggressive pigment removal. This includes:

• Cooling, calming treatments: e.g., LED therapy for inflammation, gentle enzymatic or lactic acid peels.

• Pigment suppression: Consistent use of tyrosinase inhibitors (such as azelaic acid, kojic acid, arbutin, or tranexamic acid).

• Barrier repair: A healthy skin barrier reduces inflammation and improves treatment tolerance.

• Strict light and heat protection: Physical sunscreen, wide-brimmed hats, avoiding saunas/hot yoga, and limiting midday sun exposure.

The Bottom Line

For melasma, the rule is simple: heat fuels pigment. IPL’s broad-spectrum, heat-heavy nature makes it the least appropriate choice for this condition. While some lasers, used conservatively, can help without causing rebound, no device should be used without first calming the skin, reducing melanocyte reactivity, and creating a solid pigment-control routine.

Understanding the biology of heatinduced melanogenesis gives both therapists and clients the power to make informed choices — and to avoid the frustration of treating melasma only to make it worse.

www.gwsi.com.au education@gaywardle.com