What causes dark pigmentation around the mouth?

Why pigmentation shows up specifically around the mouth

The skin around the mouth and upper lip is thin, moves constantly, and is one of the most commonly under-protected areas when it comes to sunscreen application, which is part of why discolouration tends to concentrate there rather than elsewhere on the face. There isn’t one single cause: several different conditions can produce dark patches in this exact spot, and telling them apart matters because the right response is different for each.

Melasma is one of the most common causes

Melasma frequently affects the upper lip and can create symmetrical, moustache-like shading across both sides of the mouth. It’s driven by hormonal activity and is strongly linked to melasma, frequently affecting the upper lip and perioral area, creating a moustache-like shadow, strongly influenced by hormonal changes like pregnancy and menopause, genetic predisposition and cumulative exposure to UV and visible light. Melasma is notoriously stubborn and tends to flare with heat, humidity and sun exposure, which is a particular issue in a tropical climate. See our page on the difference between pigmentation and melasma for more on why this type responds differently to treatment.

Post-inflammatory marks and irritation

Any irritation around the mouth, waxing, threading, shaving, cold sores, acne, or reactions to lip products and toothpaste ingredients, can leave behind a dark mark once the skin calms down. This is post-inflammatory hyperpigmentation, and it’s one of the most common causes of hyperpigmentation around the mouth, particularly in medium to darker skin tones, commonly developing after inflammation or skin injury including acne breakouts, perioral dermatitis, eczema and allergic reactions. It usually fades over time but can persist for months without any treatment at all.

Don’t confuse it with perioral dermatitis

Sometimes what looks like discolouration is actually a rash rather than true pigmentation. Perioral (periorificial) dermatitis is a common facial skin problem characterised by groups of itchy or tender small red papules, with the area around the eyes, nose and mouth most commonly affected, and it classically spares a thin strip of skin right at the lip border. This needs different management to pigmentation, and using strong actives on it can make things worse.

Less common but worth ruling out

Occasionally, perioral darkening is linked to nutrient deficiencies, medication side effects, smoking, or in rare cases underlying medical conditions. If pigmentation around the mouth appears suddenly, is accompanied by other symptoms, or doesn’t fit the usual pattern, it’s worth mentioning to a GP.

What actually helps

Because the cause varies so much person to person, a proper skin consultation is the most useful starting point rather than reaching for a shop-bought serum based on a guess. Sunscreen reapplied specifically over the mouth and chin area is non-negotiable regardless of cause, since UV exposure worsens almost every type of perioral pigmentation. From there, options such as targeted pigmentation treatment or light-based treatments may be discussed once melasma, PIH and dermatitis have been properly distinguished, since treating the wrong condition with the wrong tool can genuinely make pigmentation worse.