After a certain age, you started to notice dark patches developing on your skin. But they came on gradually, and didn’t really make much of a difference to your appearance. Lately, though, you’ve noticed that they’ve gotten a whole lot more noticeable. You’re wondering what might be causing them, and how you can make it better.

There are three main causes of dark spots or patches on the skin: melasma, age spots, and post-inflammatory hyperpigmentation. All are related to an overabundance of melanin, the pigment that colors your eyes, skin, and hair. They can be caused by a combination of genetic factors, sun exposure, and irritation to the skin.

But if they’re suddenly getting darker or more prevalent, it might be because you’ve changed up your routine. Or there might be another underlying factor causing more or darker patches. If you’re doing any of these things, you might be able to stop or slow the progression of your dark spots. Here are a few potential culprits that could be worsening your hyperpigmentation.

1. Sun Exposure

Some dark patches, often called sun spots or age spots, are caused by frequent or prolonged sun exposure over time. Even if your sun spots have another cause, too much time in the sun can make them more apparent. Hyperpigmentation due to melasma, for example, is linked to genes and hormones. But sun exposure can make melasma spots darker — or trigger new patches to form.

If you have dark spots for any reason, make sure to use a daily sunscreen or moisturizer with SPF. When spending prolonged time in the sun, use a high-SPF sunscreen and consider a cover-up and a wide-brimmed hat. For long beach days, stay close to that beach umbrella. Avoid sun exposure between 10 a.m. and 2 p.m. — or whatever times of day the sun’s rays are most intense in your region. 

2. Heat, Excessive Sweating, and Irritation

It’s not just direct sunlight that causes melasma spots to form or appear darker. Heat alone, even indoors, can cause your body to produce more dark spots or exacerbate the ones you have. This is thought to be because heat causes inflammation and vasodilation, both factors that increase hyperpigmentation.

Anything that causes inflammation or irritation can worsen most skin conditions. Post-inflammatory hyperpigmentation (PIH), another cause of dark spots, is actually caused by irritation or injury to the skin. But, as with other factors, irritation and inflammation can aggravate all different types of dark spots.

3. Skincare Products and Treatments

Many skincare products and treatments can heighten the visibility and frequency of dark spots. This includes some products and treatments specifically designed to make them better. Retinoids, which stimulate collagen production to lessen signs of aging, can lessen dark spots. But in some people, particularly darker-skin individuals, they can occasionally have the opposite effect.

AHAs, including glycolic acid, may sometimes be a better option for some folks with darker skin. But overusing them can also lead to more serious hyperpigmentation. Chemical peels and laser treatments, also designed to treat this issue, can likewise backfire and make it worse. In general, any skincare product that irritates the skin can also trigger dark spot flare ups.

4. Medications

A long list of medications can increase the appearance of dark spots. According to one study, medications might be responsible for up to 20% of hyperpigmentation cases. Medications that might cause or worsen dark spots include birth control pills, chemotherapy drugs, NSAIDs, antimalarials, psychotropic drugs, and tetracyclines.

If you suspect your medication might be causing dark spots, speak to your healthcare provider about switching treatments. But remember that appearance isn’t always the most important thing. You and your doctor will need to weigh the pros and cons of any important medications you’re taking. In some cases, dark spots might be a side effect worth enduring. Never stop taking your medications without consulting your provider.

5. Hormone Changes

The reason birth control pills can cause dark spots to worsen is that they contain estrogen and progesterone. These hormones, produced naturally in the body, are often at least partially responsible for the development of melasma. Taking them in pill form can cause your melasma to flare up even more.

Other hormonal changes or imbalances can also impact melasma. These include hormone disorders like polycystic ovary syndrome (PCOS). Another common hormonal change that causes or worsens dark spots is pregnancy. Some people who’ve never had melasma before develop these dark spots in their second or third trimester. A common nickname for melasma is actually “the mask of pregnancy.”

Always Check for Underlying Conditions

Other underlying medical conditions can lead to dark spots or make them worse. For example, skin conditions like acne and rosacea can intensify dark spots. Treating these conditions with appropriate dermatological therapies can lead to a reduction in hyperpigmentation, too. But sometimes, dark patches on the skin can be a sign of much more insidious illness. Dark patches that are velvety, and found on the neck, armpit or groin, could be a symptom of diabetes. If you have a spot that changes color, grows rapidly, or becomes raised, itchy, or painful, see a healthcare provider right away. It could be melanoma — a potentially deadly type of skin cancer.