What causes hyperpigmentation?

Hyperpigmentation happens when certain areas of the skin produce or hold onto more pigment than the surrounding skin.

That pigment is called melanin. Melanin is made by specialized cells called melanocytes, then transferred to surrounding skin cells where it helps give skin its colour. This process is normal and protective, especially in response to light exposure. But when melanin production becomes uneven or overactive, dark spots, patches, or uneven tone can appear.

Hyperpigmentation is not one single condition. It is a visible sign that the skin has been responding to a trigger — often light, inflammation, hormones, or injury.

The Role of Melanin

Melanin plays an important role in helping protect the skin from environmental stress, especially ultraviolet radiation. When skin is exposed to UV light, melanocytes are stimulated to produce more melanin.

This is why sun exposure can deepen existing dark spots and contribute to new areas of uneven tone.

In simple terms: hyperpigmentation forms when the skin’s pigment system becomes overactive in specific areas.

Common Causes of Hyperpigmentation

1. Sun Exposure

Sun exposure is one of the most common triggers for hyperpigmentation.

Ultraviolet light stimulates melanogenesis — the process of melanin production. Over time, repeated UV exposure can cause pigment to become more concentrated in certain areas, leading to sun spots, uneven tone, and darkened patches.

Visible light may also contribute to pigmentation, especially in deeper skin tones and in conditions such as melasma.

This is why daily sunscreen is one of the most important steps in any routine for uneven tone.

2. Inflammation

Inflammation can also trigger excess pigment.

This is called post-inflammatory hyperpigmentation, or PIH. It can appear after acne, irritation, eczema, injury, aggressive exfoliation, or other forms of skin stress.

When the skin becomes inflamed, it releases signals that can stimulate melanocytes. As the visible irritation fades, pigment may remain behind as a brown, tan, grey-brown, or dark mark.

This is especially common in medium to deep skin tones, where melanocytes may be more reactive to inflammation.

3. Hormonal Changes

Hormonal changes can also influence pigmentation, particularly in melasma.

Melasma is a form of hyperpigmentation that often appears as larger, symmetrical patches on areas like the cheeks, forehead, upper lip, or jawline. It is commonly associated with sun exposure, hormonal shifts, pregnancy, oral contraceptives, and genetic predisposition.

Melasma is complex because it is not caused by one factor alone. Light exposure, hormones, inflammation, vascular changes, and skin barrier stress may all contribute.

4. Skin Injury or Irritation

Any injury or irritation to the skin can potentially lead to pigmentation.

This can include blemishes, scratches, burns, picking at the skin, over-exfoliation, or using products that are too harsh for the barrier.

For sensitive or reactive skin, this matters. A brightening routine should not rely only on strong actives. It should also help keep the barrier calm and supported, because repeated irritation can make uneven tone harder to improve.

5. Genetics and Skin Tone

Genetics influence how much melanin the skin naturally produces and how reactive pigment cells are to triggers like light and inflammation.

People with more melanin-rich skin may be more prone to visible post-inflammatory hyperpigmentation after acne, irritation, or injury. This does not mean hyperpigmentation is permanent, but it can take longer to fade and requires a more consistent, barrier-supportive approach.

Why Hyperpigmentation Can Be Difficult to Treat

Hyperpigmentation can be slow to fade because pigment is part of the skin’s biological response system.

If the original trigger continues — such as unprotected sun exposure, recurring acne, irritation, or barrier disruption — the skin may keep producing pigment faster than it can visibly fade.

That is why an effective approach should focus on three things:

Reducing the trigger
Supporting the skin barrier
Using brightening ingredients consistently and gently

The goal is not to force the skin into change. The goal is to create the conditions for more even-looking, resilient skin over time.

A Barrier-First Approach to Uneven Tone

At TSOS™, we believe uneven tone should be approached with respect for the skin barrier.

Brightening ingredients can be helpful, but they work best when the skin is supported, hydrated, and calm. For skin that is sensitive, dry, reactive, or easily irritated, this is especially important.

A thoughtful routine for hyperpigmentation should include:

Daily broad-spectrum sunscreen
Barrier-supportive hydration
Gentle, consistent brightening ingredients
Avoiding unnecessary irritation
Patience and long-term consistency

Hyperpigmentation does not usually appear overnight, and it does not usually resolve overnight. But with a steady, barrier-first approach, the skin can gradually look clearer, calmer, and more even.

The TSOS™ Philosophy

Hyperpigmentation is often treated as a surface concern, but it begins with the skin’s response to stress.

Light, inflammation, hormones, and irritation can all influence how pigment is produced and distributed. That is why we approach uneven tone through both targeted brightening and barrier support.

Because resilient skin is better prepared to recover, rebalance, and visibly improve over time.

Reviewed by Connor Greig, P.Chem
Professional Chemist and Founder, TSOS Skincare

Sources:

Yardman-Frank, J. M., & Fisher, D. E. Skin pigmentation and its control: From ultraviolet radiation to stem cells. Experimental Dermatology, 2021.

Davis, E. C., & Callender, V. D. Postinflammatory hyperpigmentation: A review of the epidemiology, clinical features, and treatment options in skin of color. The Journal of Clinical and Aesthetic Dermatology, 2010.

Ogbechie-Godec, O. A., & Elbuluk, N. Melasma: An up-to-date comprehensive review. Dermatology and Therapy, 2017.