Skin discoloration: causes and when to worry

Skin discoloration is a broad term for patches of skin that are darker or lighter than the skin around them. Most causes are harmless, and many fade on their own. A few need a doctor. This guide sorts the common causes by what they look like and explains when to get a patch checked. It belongs to Skinli's guide to hyperpigmentation.

What skin discoloration means

MedlinePlus, the health library of the U.S. National Library of Medicine, defines abnormally dark or light skin as skin that has turned darker or lighter than normal. Skin gets its color from melanin, a pigment made by cells called melanocytes.

MedlinePlus uses three terms:

• Hyperpigmented skin has too much melanin, so it looks darker.
• Hypopigmented skin has too little melanin, so it looks lighter.
• Depigmented skin has no melanin at all, so it looks white.

Not every color change comes from melanin. MedlinePlus says patchy skin can also come from changes in blood vessels, from bacteria or other organisms growing on the skin, and from inflammation due to rashes.

Causes of darker patches

MedlinePlus lists these causes of hyperpigmentation. The details beside each one come from MedlinePlus and the American Academy of Dermatology (AAD).

Cause	What it looks like	More in this hub
Inflammation, such as acne	Flat marks where the skin was inflamed	Dark marks after pimples
Sun exposure	Flat brown spots on skin that got the most sun	Sun spots
Pregnancy and hormones	Brown patches on both sides of the face (melasma)	Melasma
Certain medicines	Darkening linked to medicines such as minocycline, some cancer medicines and birth control pills	Ask the prescribing doctor
Acanthosis nigricans	Dark, thick, velvety skin in body folds	See a doctor
Hormone conditions, such as Addison disease	Darkening of the skin	See a doctor
Iron overload (hemochromatosis)	Darkening of the skin	See a doctor
Certain birthmarks	Present from birth or early life	See a doctor if it changes

The AAD adds that on medium and darker skin, dark spots often appear after a cut, burn or insect bite heals, or when a skin or hair product irritates the skin.

Dark, velvety skin in body folds

One pattern deserves its own mention. MedlinePlus describes acanthosis nigricans as darker, thick, velvety skin in body folds and creases, such as the armpits, groin and neck. It can occur in healthy people, but it can also be linked to hormone imbalances in diabetes and obesity, often called insulin resistance. MedlinePlus says some medicines and some cancers can also cause it, and that fast, widespread patches should be checked for a link to cancer. MedlinePlus says to contact your provider if you develop these areas, and that the patches often disappear if the cause is found and treated.

Causes of lighter patches

MedlinePlus lists these causes of hypopigmentation:

• Inflammation. Skin can lose color after inflammation, just as it can gain color. The AAD says some people get white or light flat spots after acne, which usually fade over time.
• Tinea versicolor. A fungal infection that can appear as lighter patches. MedlinePlus says it often returns even with treatment.
• Pityriasis alba. A skin condition that MedlinePlus lists among the causes of pale patches.
• Vitiligo. The NHS describes it as a long-term condition in which pale white patches develop because the skin lacks melanin. It says the patches are usually permanent, and that pale areas burn easily in the sun.
• Certain medicines and birthmarks.

A light patch needs a diagnosis before treatment, because the causes need different care. An antifungal lotion helps tinea versicolor, for example, and does nothing for vitiligo.

Everyday causes that are easy to fix

Some discoloration comes from daily habits, and changing the habit stops new patches.

• Uneven sunscreen. MedlinePlus lists unevenly applied sunscreen among the causes of patchy color, because it leaves areas of burn, tan and no tan side by side. Cover every part of the skin that clothing does not.
• Products that irritate. The AAD says a skin or hair care product that irritates the skin can cause dark spots, especially on medium and darker skin. It suggests gentler products, often labeled "for sensitive skin" or "fragrance-free." Once the irritation stops, new spots tend to stop appearing.
• Strong acne or anti-aging products used too fast. The AAD says irritation from a retinoid can trigger dark marks on skin of color, and that a slow start with moisturizer helps prevent this.
• At-home peels and devices. On darker skin, the AAD says even at-home chemical peels, microdermabrasion and laser devices can cause permanent dark marks and light spots.
• Picking and scratching. Each injury to the skin can leave a mark as it heals. The AAD says a spot left by an injury fades in time if the skin is not hurt again.

Discoloration and skin tone

Skin tone changes both the risk and the look of discoloration. MedlinePlus says lighter skin is more sensitive to sun damage, which raises the risk of skin cancer, while darker skin is still at risk from too much sun. It also says that in darker-skinned people, skin damage may cause permanent hyperpigmentation. The AAD says dark spots and patches are one of the most common reasons people with darker skin tones see a dermatologist. The page on dark spots on darker skin covers the extra care that helps.

Is it harmful?

For most people, no. MedlinePlus says skin color changes are generally cosmetic and do not affect physical health, though they can cause stress. Some pigment changes, it adds, may be a sign of risk for other medical problems.

Melanoma, a skin cancer, is on the MedlinePlus list of causes of pigment changes. The AAD says it can look like a changing mole, or a spot that looks like a new mole, freckle or age spot but looks different from your other spots. Color change on its own is rarely cancer. Change over time is what needs checking.

When to see a doctor

MedlinePlus advises an appointment for:

• Skin discoloration that causes you significant concern
• Persistent darkening or lightening of the skin that has no clear reason
• Lasting color changes with no known cause
• A new mole or other growth
• A growth or sore that changes color, size, shape or appearance, which may be a sign of skin cancer

The NHS adds a mole that is painful, itchy, bleeding or crusty, and a new or unusual mark that has not gone away after a few weeks. For the warning signs of melanoma in detail, read when a dark spot needs a doctor.

How a doctor finds the cause

MedlinePlus says your provider will examine your skin and ask questions such as:

• When did the color change start, and did it start suddenly?
• Is it getting worse, and how fast?
• Has it spread to other parts of the body?
• What medicines do you take?
• Has anyone in your family had the same problem?
• How much time do you spend in the sun, and do you use tanning beds?

Tests can include a Wood lamp exam, which uses ultraviolet light; a scraping of the skin to look for a fungus; a biopsy, which is a small skin sample; and blood tests, such as iron or thyroid tests.

What helps

Treatment depends on the cause. MedlinePlus says some color changes return to normal without treatment. For darker patches, these steps help in most cases:

• Treat the cause. The AAD says that for dark spots caused by a skin condition, you must treat the condition first. MedlinePlus says acanthosis nigricans often fades once its cause is treated.
• Protect the skin from sun. MedlinePlus advises sunscreen of SPF 30 or higher, and warns that hyperpigmented skin may get even darker in the sun. In darker-skinned people, it says, skin damage may cause permanent hyperpigmentation.
• Use a fading ingredient for dark spots. The AAD lists azelaic acid, glycolic acid, kojic acid, retinoids and vitamin C.
• Cover it if you want to. MedlinePlus says cosmetics and skin dyes can hide color changes.

Be careful with bleaching creams. MedlinePlus advises checking with your provider first about safety and how long to use them. The FDA says no skin lightening product is legally sold over the counter in the US, and it has received reports of rashes, facial swelling and permanent skin discoloration from hydroquinone products. MedlinePlus also lists long-term hydroquinone use itself as a cause of pigment changes.

For a step-by-step plan for dark spots on the face, read how to get rid of dark spots on your face.