Skin Education
Sun, inflammation, hormones, and injury — the four root causes, how each one triggers excess pigment, and why location on the body usually tells you which is at play.
Hyperpigmentation is caused by the skin overproducing melanin. The four main triggers are sun exposure, inflammation, hormones, and skin injury — and anything that stimulates the pigment cells can leave an area darker than the surrounding skin.
This guide explains the root causes, why hyperpigmentation shows up in specific places on the body, and how everyday habits like shaving and certain skincare can contribute.
If you want a broader overview of [what hyperpigmentation is], read our full guide.
The Four Main Causes§
What Are the Main Causes of Hyperpigmentation?§
The main causes of hyperpigmentation are sun exposure, inflammation, hormonal changes, and skin injury — all of which push melanocytes to overproduce melanin. Most people's pigmentation traces back to one or more of these, and sun exposure ties them together by worsening them all.
The biggest single cause. Stimulates melanin production immediately — and cumulatively over years. Also darkens every other type of existing pigmentation, which is why unprotected sun undoes any progress on fading spots.
Acne, eczema, irritation, or any injury can leave post-inflammatory marks as the skin heals. The melanocytes at the site of inflammation produce excess pigment as part of the repair process.
Hormonal shifts — especially in pregnancy or with hormonal medication — drive melasma by stimulating melanocytes. The result is typically a larger, more diffuse patch rather than an individual spot.
Physical trauma to the skin, from a cut to repeated friction, can trigger pigment as it repairs. This is why areas prone to rubbing and shaving are common sites for hyperpigmentation.
Does the Sun Cause Hyperpigmentation?§
Yes — sun exposure is the leading cause of hyperpigmentation. Ultraviolet light stimulates the skin to produce more melanin, both immediately as a tan or a fresh spot, and cumulatively over years as sun spots and age spots. Not sure if your marks are sun spots or freckles? Read our guide to [Sun Spots vs. Freckles].
UV also darkens every existing type of pigmentation — from post-acne marks to melasma — which is why unprotected sun undoes progress on fading spots regardless of what is causing them.
Sun exposure is also the most preventable cause of hyperpigmentation. Daily broad-spectrum SPF is the single most valuable step for both preventing and treating it.
The SPF Rule
Every type of hyperpigmentation is worsened by UV. Daily SPF is not just prevention — it is treatment.
Why Do I Have Hyperpigmentation in Specific Areas?§
Hyperpigmentation often develops in specific areas because each location has its own common trigger — usually friction, hair removal, hormones, or sun exposure. Understanding the local trigger helps you address it directly.
To better recognize the patterns, see [what hyperpigmentation looks like] in different areas.
Hormones and hair removal are the most frequent causes. Both can stimulate excess pigment in the sensitive skin of this area.
Friction and shaving create irritation that leaves post-inflammatory marks. Reducing friction and changing hair-removal methods often makes the biggest difference.
Sun exposure, acne, and friction from clothing or jewelry all contribute to darkening along the neck, particularly at the sides and back.
Rubbing and inflammation play a role. True pigmentation here tends to appear brownish — purple or blue tones are more often vascular, not melanin-related.
Typically hormonal — melasma tends to appear as larger, symmetrical patches on the upper face, often triggered by pregnancy or hormonal contraception.
Cumulative sun exposure throughout life. An area that is easy to overlook when applying SPF — and one that accumulates spots steadily over years. If you are noticing small brown marks in sun-exposed areas, learn the difference between [sun spots and freckles].
Do Shaving and Waxing Cause Hyperpigmentation?§
Yes — shaving and waxing can cause hyperpigmentation, because they create micro-trauma and inflammation that can trigger post-inflammatory pigment. This is particularly common in the bikini line, underarms, and legs, and the risk is higher on medium to deep skin tones.
- Exfoliate gently and regularly to prevent ingrown hairs
- Use a sharp, clean razor and shave in the direction of growth
- Soothe the skin immediately after removal
- Avoid sun on freshly shaved or waxed areas
- If a method keeps causing marks, consider switching or seeking professional alternatives
Can Skincare and Treatments Cause Hyperpigmentation?§
Certain skincare ingredients and treatments can cause hyperpigmentation — but usually only through misuse, over-exfoliation, or irritation rather than any inherent danger.
Using strong acids too frequently, or using too many actives at once, can irritate the skin enough to trigger post-inflammatory pigment. The fix is not to avoid actives — it is to introduce one at a time and avoid over-exfoliating.
Poorly formulated or oxidized products can irritate the barrier and trigger pigment. Fragrance, denatured alcohol, and high-concentration exfoliants are the most common culprits on sensitive skin.
In-office treatments can trigger pigment if not tailored to the skin tone and condition — particularly on deeper skin tones. Choosing an experienced provider makes a significant difference.
Most pigmentation has a clear cause — and once you identify it, you can address it with the right combination of protection, treatment, and professional guidance.
FAQ§
What causes hyperpigmentation?
Excess melanin production, triggered mainly by sun exposure, inflammation such as acne, hormonal changes, and skin injury or friction. For a broader overview, read [What Is Hyperpigmentation?]
What causes hyperpigmentation on the face?
Most often sun exposure, post-acne inflammation, and hormonal melasma. These tend to appear on the cheeks, forehead, and upper lip in characteristic patterns.
You can also see [what hyperpigmentation looks like on the skin] in our visual guide.
Does shaving cause dark spots?
It can. Shaving creates micro-irritation that can trigger post-inflammatory pigmentation, especially on the bikini line, underarms, and legs — and particularly on deeper skin tones.
What causes hyperpigmentation around the mouth?
Commonly hormones and hair removal, both of which can stimulate excess pigment in the sensitive skin around the mouth and upper lip.
Why do I have hyperpigmentation on my inner thighs?
Friction from movement and clothing, along with shaving, irritates the skin and can trigger post-inflammatory pigmentation in that area.
Can skincare cause hyperpigmentation?
Yes, but usually through over-exfoliation or irritation rather than inherent risk. Used correctly — one active at a time, no over-exfoliating — actives help rather than harm.