What causes differences in vulvar and genital skin pigmentation, and how is it related to a person's overall skin tone o

The short version

• There is no single "normal" color for the vulva or genitals. The skin of the labia, scrotum, and anus is often darker than skin elsewhere on the body, and that is considered perfectly normal [52][55][58]. Color varies from person to person, though it tends to be darker than other areas [54][57][59].
• Vulvar color does not always match whole-body skin color. A dark-skinned person can have a lighter vulva, and a light-skinned person can have dark brown labia [1]. Still, natural skin tone and skin type do influence how dark the area looks [35][36][116].

Why genital skin tends to be darker

• Skin color comes from melanin, and vulvar skin contains this pigment [14]. "Hyperpigmentation" just means more pigment, so areas of the vulva become darker in color [15][136].
• The amount of color in skin depends on the density of melanocytes (pigment-making cells), how much melanin each cell makes, and how pigment packets are transferred to surrounding skin cells [81].
• Genital tissue has a higher density of melanocytes than many other body sites; one source says about 50% more per unit area than truncal skin [80][121]. That higher density helps explain why genital skin is often darker, especially because sex hormones can darken it further [84].
• Skin color naturally differs by body area. Darkening can also happen on the face, chest, back, arms, elbows, knees, underarms, and knuckles, and pregnancy can darken nipples, areolae, moles, and the linea nigra [60][61][64].

Main causes of vulvar and genital darkening

• Hormones are a major cause. Estrogen and progesterone regulate melanin production; estrogen increases pigment production, while progesterone decreases it [20][23]. Melanocytes around the vulva, nipples, and anus are especially sensitive to hormones, and rising hormone levels can push melanin production into overdrive [30][88]. This can happen during puberty, pregnancy, menopause, or with birth control, and the genital area gradually darkens in response to hormonal changes over time [40][43][98][122]. Darkening from puberty or pregnancy often stays or increases rather than going away [41][44].
• Aging is another common cause. Darkening in the genital area usually comes with age because skin has experienced years of repeated trauma or hormonal changes [49][50]. Older age can darken the vulva in spots or patches, especially where there are folds or creases [95][96].
• Friction, shaving, waxing, ingrown hairs, infections, and inflammation can darken skin. Friction can make melanocytes hyperactive, and things like sexual activity, tight underwear, hair removal, yeast infections, ingrown hairs, and folliculitis can trigger post-inflammatory hyperpigmentation [18][33][71][74][76][91].
• Some skin conditions cause dark patches. Acanthosis nigricans, linked with PCOS, diabetes, obesity, or certain medications, can create dark, velvety, leathery patches on the vulva [4][101][128][129]. Post-inflammatory hyperpigmentation on the vulva can follow inflammatory skin disease, trauma, dermatologic treatments, or fixed drug eruption [126]. Endocrine conditions like congenital adrenal hyperplasia, Addison's disease, or Cushing's disease can cause similar darkening [124].
• Vulvar melanosis is a common brown/black pigmented change. Its cause is not fully understood, but researchers have proposed links to hormonal status, lichen sclerosus, and HPV infection [7][8][105][112]. It accounts for most pigmented vulvar lesions [104].
• Rarely, a new spot can be a warning sign. Vulvar cancer can look like a red, white, or dark brown spot or patch that is distinctly different from the surrounding skin [6][103]. Hyperpigmented anogenital warts are also possible, especially in darker skin types [130].

How overall skin tone and race fit in

• Natural skin tone matters, but it is not a simple rule. Melanocyte density does not vary much by racial background overall, but it does vary by body site [80]. The exact hue of physiological genital hyperpigmentation varies across racial groups and also from person to person within the same group [83].
• Genetic factors, including variability among racial groups, combine with hormones and acquired factors such as ultraviolet light, inflammation, and HPV infection to affect increased genital pigmentation [82].
• Physiologic hyperpigmentation is a normal variant most common in darkly complexioned individuals. It typically shows up on the labia minora, posterior introitus or fourchette, and perianal skin, and it can also affect the hair-bearing labia majora and inner thighs [85][118][119][120][132].
• Post-inflammatory hyperpigmentation is more common in naturally darker skin, independent of ethnicity, and is most striking in people of color [86][125]. In darker skin types, even active inflammation can look pigmented [127].
• Vulvar hyperpigmentation can happen in all skin types, and normal genital skin variations may be counted among pigmented vulvar lesions, which are often shades of brown and flat in appearance [113][114][115].
• How a vulvar condition looks can depend on skin tone. For example, in lichen sclerosus, hyperpigmentation may look darker brown or dark purple in light brown skin and red in lighter skin [12][133].