Dark Spots on Skin: Causes and How to Fade Them

Why dark spots form

Melanocytes in the skin make melanin to protect against UV light. Dark spots appear when melanocytes make too much melanin in one area, or when they multiply. Triggers include UV light, hormones, inflammation, injury and certain medicines. People with darker skin tones are more prone to long-lasting marks after inflammation, because their melanocytes respond more strongly.

Common types of dark spots

Sun spots and age spots

Age spots, also called liver spots though they have nothing to do with the liver, are the result of years of UV exposure. They are harmless, but they mark sun-damaged skin. A sun spot that darkens unevenly or grows on the face of an older person should be checked for lentigo maligna, an early melanoma.

Melasma

Melasma is triggered by sunlight, visible light and hormones. It often appears in pregnancy ("mask of pregnancy") or with birth control pills and can last for years. Heat and visible light from screens or sunlight through windows can worsen it, so tinted mineral sunscreen helps.

Marks after acne, eczema or injury

Post-inflammatory hyperpigmentation follows anything that inflames the skin: acne, eczema, insect bites, burns, shaving bumps or harsh treatments. Marks in the upper skin layer fade in 3 to 12 months. Deeper gray-blue marks may last years.

Medical and other causes

• Acanthosis nigricans: a sign of insulin resistance, prediabetes or polycystic ovary syndrome
• Medicines: minocycline, amiodarone, some chemotherapy drugs, antimalarials, and hormones. Some medicines and perfumes cause dark patches after sun exposure (photosensitivity)
• Tinea versicolor: a yeast infection causing light or dark, slightly scaly patches on the chest and back
• Addison's disease and hemochromatosis: cause widespread darkening, not single spots
• Café-au-lait spots: light brown birthmarks. Six or more larger ones can suggest neurofibromatosis
• Pregnancy: darkening of the nipples, genitals and a line down the belly (linea nigra) is normal

When a dark spot could be skin cancer

Melanoma can arise in a new spot or an existing mole. Use the ABCDE checklist:

• Asymmetry: one half does not match the other
• Border: ragged, notched or blurred edges
• Color: several shades of brown, black, red, white or blue
• Diameter: larger than 6 mm, though melanomas can be smaller
• Evolving: any change in size, shape, color, height, or new itching or bleeding

Also watch for the "ugly duckling", a spot that looks different from your other moles. Melanoma in people with darker skin is more often on the palms, soles and under the nails.

How doctors diagnose dark spots

A dermatologist examines the spot, often with a dermatoscope, a handheld magnifier with a light. A Wood's lamp shows how deep the pigment is and helps identify tinea versicolor. A skin biopsy is taken from any spot that looks suspicious. Blood tests for blood sugar, hormones or adrenal function are done when the pattern suggests a medical cause.

How to get rid of dark spots

Sun protection comes first

No treatment works without daily sun protection. Use a broad-spectrum SPF 30 or higher sunscreen every day, reapply every 2 hours outdoors, and wear a wide-brimmed hat. For melasma, a tinted sunscreen with iron oxides also blocks visible light.

Topical treatments

• Hydroquinone: the most studied lightening agent. Over-the-counter strengths in some countries, higher strengths by prescription. Use only for limited periods as directed.
• Retinoids: tretinoin, adapalene or retinol speed skin turnover.
• Azelaic acid: helps acne marks and melasma and is safe in pregnancy.
• Vitamin C, niacinamide, kojic acid and tranexamic acid: milder options, useful for maintenance.
• Triple combination cream (hydroquinone, tretinoin and a mild steroid) for melasma, by prescription.

Expect visible improvement after 8 to 12 weeks.

In-office treatments

• Chemical peels (glycolic, salicylic or trichloroacetic acid)
• Laser and intense pulsed light for sun spots. These must be used cautiously in darker skin and melasma, because they can make pigmentation worse.
• Cryotherapy (freezing) for individual age spots and seborrheic keratoses

What to avoid

Do not use mercury-containing or unregulated "skin bleaching" creams, which can cause poisoning. Avoid picking at acne and harsh scrubs that inflame the skin and create new marks.

Frequently asked questions

What causes dark spots on the skin?

The commonest causes are sun damage, melasma from hormones and sunlight, marks left after acne or other inflammation, and freckles. Medicines, insulin resistance and some hormonal conditions can also darken the skin. Rarely, a new or changing dark spot is melanoma.

How long does it take for dark spots to fade?

Marks from acne or injury fade in 3 to 12 months on their own, faster with treatment. Sun spots and melasma usually need treatment, with improvement after 2 to 3 months. Without daily sunscreen, spots tend to return.

Are dark spots on the skin dangerous?

Most are harmless. See a doctor if a spot is new after age 30, changing, irregular in shape or color, larger than a pencil eraser, or bleeding, or if your skin is darkening all over with tiredness or weight loss.

What is the best treatment for dark spots on the face?

Daily broad-spectrum sunscreen plus a topical treatment such as hydroquinone, a retinoid or azelaic acid works for most facial spots. A dermatologist can add peels, lasers or prescription creams. Melasma needs gentle, long-term treatment because it easily comes back.

Can dark spots be a sign of diabetes?

Yes, in one pattern. Velvety, thickened dark skin in the neck folds, armpits or groin, called acanthosis nigricans, is a sign of insulin resistance and prediabetes. Ask your doctor for a blood sugar test if you notice it.