Brown spots appear when clusters of skin cells produce extra melanin, the pigment that gives skin its color. The most common cause is cumulative sun exposure, but hormones, medications, skin injuries, and even vitamin deficiencies can trigger them too. Most brown spots are harmless, though certain changes in size, shape, or color deserve a closer look.
How Brown Spots Form
Your skin contains specialized cells that produce melanin, which absorbs UV light and protects your DNA from radiation damage. When skin is exposed to UV rays, DNA damage in those cells activates a signaling chain that ramps up melanin production. Over time, this pigment doesn’t always distribute evenly. It can concentrate in patches, leaving you with flat brown spots, freckle-like clusters, or larger blotchy areas.
This process explains why brown spots tend to show up on areas that get the most sun: the face, neck, chest, shoulders, backs of the hands, and forearms. But UV exposure isn’t the only trigger. Anything that causes inflammation or hormonal shifts can push melanin production into overdrive in localized areas.
Sun Damage (Age Spots)
The spots most people notice first are solar lentigines, commonly called age spots or liver spots. They’re flat, tan to dark brown, and range from the size of a freckle to about a centimeter across. Despite the nickname, they’re caused by years of sun exposure rather than aging itself. That said, they tend to multiply after age 40 simply because the skin has accumulated more UV damage by that point.
These spots are permanent without treatment. They won’t fade on their own because the underlying melanin-producing cells have been permanently altered. New ones will continue to appear on sun-exposed skin if you don’t protect it.
Melasma and Hormonal Spots
If you’re noticing larger, blotchy brown patches rather than small defined spots, melasma is a likely explanation. Melasma produces uneven patches and freckle-like spots that typically appear on the face, neck, and arms. It’s driven by hormonal changes, particularly increases in estrogen and progesterone.
Common triggers include pregnancy (sometimes called “the mask of pregnancy”), birth control pills, and thyroid problems. Some research also links it to stress, since elevated cortisol levels may contribute. Melasma is far more common in women, though men can develop it too. Sun exposure makes it worse, which is why it often flares in summer and partially fades in winter.
Spots After Skin Injuries
Brown marks that appear where you previously had a pimple, cut, burn, rash, or bug bite are called post-inflammatory hyperpigmentation. The inflammation from the injury stimulates extra melanin production in that area, leaving a dark mark behind after the wound itself has healed.
This type of spotting is especially common after acne and tends to be more noticeable in darker skin tones. The timeline for fading varies widely. In a large study of acne-related dark marks, more than half of people still had visible spots after a year, and about 22% still had them after five years. Superficial marks on lighter skin often fade faster, sometimes within a few months, while deeper pigment changes can linger much longer without treatment.
Seborrheic Keratoses
Not all brown spots are flat. Seborrheic keratoses are raised, waxy or scaly growths that range from light tan to brown or black. They look as if they were dripped onto the skin by a candle, with a characteristic “pasted on” appearance. They’re typically round or oval and show up most often on the face, chest, shoulders, and back.
These growths are extremely common in middle-aged and older adults and are completely benign. They can look alarming because of their rough texture and dark color, but they’re not related to sun damage or skin cancer. They don’t require treatment unless they’re irritated by clothing or you want them removed for cosmetic reasons.
Medications That Cause Brown Spots
Certain medications can darken skin as a side effect. Common culprits include some antibiotics (particularly minocycline and doxycycline), antimalarial drugs like hydroxychloroquine, the heart medication amiodarone, certain blood pressure pills, and anti-inflammatory drugs. Some of these medications make your skin more sensitive to sunlight, leading to pigmentation changes in sun-exposed areas. Others deposit pigment directly in the skin regardless of sun exposure.
If you’ve started a new medication in recent months and are noticing new dark patches, it’s worth checking the side effect profile. Drug-related skin darkening often fades after stopping the medication, though it can take months.
Vitamin B12 Deficiency
A less commonly known cause is vitamin B12 deficiency, which can produce darkening of the skin, particularly in the creases of the palms, on the tops of the hands and feet, in skin folds, inside the mouth, and around recent scars. The exact mechanism isn’t fully understood, but the connection is well documented. The good news is that this type of hyperpigmentation reverses with B12 supplementation.
When a Brown Spot Could Be Melanoma
Most brown spots are harmless, but melanoma, the most dangerous form of skin cancer, can look like an ordinary brown spot in its early stages. The National Cancer Institute recommends checking your spots using the ABCDE criteria:
- Asymmetry: one half of the spot doesn’t match the other half
- Border: edges are ragged, notched, or blurred, or pigment seems to spread into surrounding skin
- Color: multiple shades of brown, black, or tan within the same spot, or areas of white, gray, red, pink, or blue
- Diameter: larger than about 6 millimeters (roughly the size of a pencil eraser), though melanomas can be smaller
- Evolving: the spot has changed in size, shape, or color over recent weeks or months
Any spot that meets one or more of these criteria deserves a professional evaluation. A spot that’s growing, bleeding, itching, or looks noticeably different from your other spots is also worth getting checked.
How to Fade Existing Brown Spots
For sun spots and mild hyperpigmentation, several topical ingredients can gradually lighten dark areas. Azelaic acid (available over the counter at 10% and by prescription at higher concentrations) is effective for both dark spots and acne marks. Kojic acid, glycolic acid, and vitamin C serums also help by slowing melanin production or accelerating skin cell turnover. Prescription-strength options include hydroquinone and retinoids, which can fade spots over several months of consistent use, though they may cause temporary redness, dryness, or irritation.
For stubborn or deeper pigmentation, professional treatments offer faster results. Laser and intense pulsed light therapies can destroy excess pigment-producing cells without damaging the skin’s surface, typically requiring two to three sessions. Chemical peels remove the top layers of skin so new, more evenly pigmented skin can replace them. Cryotherapy uses liquid nitrogen applied briefly to individual spots, destroying the extra pigment so the area heals lighter. Each of these carries some risk of temporary skin color changes, so they’re best done by an experienced dermatologist, especially on darker skin tones.
Preventing New Spots
Sunscreen is the single most effective tool for preventing new brown spots and keeping existing ones from darkening. Use SPF 30 or higher on any skin that will be exposed, and reapply every two hours while outdoors. Higher SPF numbers provide more protection while the sunscreen is on, but they don’t last any longer. If you’re swimming, reapply after about 45 minutes to an hour in the water, and again after toweling off. Heavy sweating can also dilute sunscreen within an hour.
Consistency matters more than anything else here. Daily sunscreen use, even on cloudy days and even if you’re only outside briefly, is what prevents the cumulative UV damage that drives most brown spots. A wide-brimmed hat and sun-protective clothing add another layer of defense for your face, neck, and chest, the areas most prone to visible spotting.