During pregnancy, many people develop a dark, vertical line on their abdomen. This line is called a linea nigra. It’s most often shows up around the middle of the pregnancy.

Those who are pregnant aren’t the only ones who can develop this darkened line. In fact, research suggests men, children, and unpregnant women can develop the line, too.

Why does the linea nigra develop? What can be done about hiding or removing the dark line on your stomach? Read on to find out why the linea nigra develops and what it can mean.

Linea nigra is a dark, brownish line that runs vertically on an abdomen. It is typically no more than 1/4- to 1/2-inch wide, though in some people it can be wider.

Most often, the line is visible between the belly button and the pubic area. However, it can be visible above the belly button into the upper abdomen.

The linea nigra most often appears during pregnancy, but the line is actually always present. When it’s not visible, it’s called the linea alba. During pregnancy, the line can darken and become more obvious.

Research in one study revealed that 92 percent of pregnant females developed the dark line. In the same age group, 16 percent of nonpregnant females did, too. What’s more, men and children in this study also showed the darkened line. So, linea nigra isn’t unique to pregnancy.

It’s not known why the linea alba grows darker during pregnancy or outside of pregnancy. Doctors have a good guess: hormones.

Hormones are a contributing factor

Indeed, hormones can contribute to a great number of changes in both pregnant and nonpregnant bodies. It’s believed that a combination of estrogen and progesterone cause the body’s melanocytes, or melanin-producing cells, to form more melanin.

Melanin is the pigment responsible for darker skin tones and tans. With more melanin, your skin darkens. That may include often hidden, or lighter, parts of skin, such as the linea alba.

Medications and environment may also play a role

For those who aren’t pregnant, birth control pills, certain medications, and some health conditions can cause changes in hormone levels.

Exposure to the sun may also ramp up melanin production. While the sun’s rays make exposed skin darker, it can make certain parts of your skin, like the linea alba, even darker.

Underlying hormonal conditions may also be to blame

If you’re worried that an underlying medical condition may be causing the brownish line on your stomach, talk with a doctor.

Some hormonal conditions may be to blame for irregular hormone levels. Diagnosing them may help erase the brownish line on your belly. It may also help treat other symptoms and signs that are less visible.

You may think the dark line running up your stomach is unsightly. The good news is, a linea nigra is not harmful. Treatment isn’t necessary.

Time may fade it

In fact, the line may fade on its own. With time, it may return to a lighter color that’s not visible or is less prominent.

The line may reappear from time to time, too. Changes in hormones or medication may increase melanin production. These factors are often beyond your control.

Sunscreen may prevent it from becoming darker

There’s one element you can control, however. Sun exposure causes your skin cells to produce more melanin. That’s why your skin becomes darker when you’re outside. Wearing sunscreen helps protect your skin.

Applying sunscreen to your abdomen when you’re outside, especially if your skin is exposed, may prevent the line from becoming darker. Sunscreen use is also important to prevent other skin issues, like skin cancer and sunburns.

Use makeup, not bleach, on your skin

Bleaching skin isn’t recommended. It doesn’t produce good results and improper use can cause side effects like skin irritation and chemical burns.

If the visible line is problematic, you can use makeup to temporarily cover or camouflage the line.

A dark, vertical line on your stomach is called a linea nigra. A linea nigra is very common for pregnant people. It’s less common but does develop in men, nonpregnant women, and even children.

A linea nigra isn’t harmful. It’s likely caused by shifts in hormones. The increase in hormones causes melanin-producing cells in the skin to produce more pigment. Because the linea alba is always present (it’s just too light to be seen), the increased pigment makes the line very obvious.

For most people, the line will disappear on its own. There’s no treatment, but if you’re concerned about underlying issues that may be causing the dark line, talk with a doctor. They can help rule out issues that may be contributing to fluctuating hormone levels.