A big part of having a human body means constantly questioning why some sort of liquid is coming out of a certain hole at a certain time. Some stuff is normal (you get a cut and you bleed, for instance) and other stuff, like discharge coming from the nipple, can be disconcerting.

Let's start with a fun fact. Most nipples, if stimulated for long enough, will eventually produce some yellow or grayish discharge (more on that later). But spontaneous discharge, or fluid that comes out of one or both nipples without any provocation, should be a reason to visit a doctor. In rare cases, it's an early sign of breast cancer. And in less rare cases, it's a sign you just need a better sports bra. Here's what you need to know about nipple discharge.

If the discharge is yellow, gray, or green

The best way to break this down is by color, because that's the first thing you'll probably notice when you see liquid coming from your nipple — also because different colors signal different underlying causes. Dr. Rebecca Brightman, an ob-gyn in New York City, said yellow, green, or gray-ish discharge is typically just dead skin cells from within the breast. Other "totally benign changes" in the breast like duct ectasia — a condition that occurs when a milk duct's walls thicken, resulting in fluid build-up — can also cause yellow, green, or gray-ish discharge. But even though most of these conditions don't increase risk for cancer, Brightman still said you should address discharge-causing conditions with your doctor.

Dr. Therese Bevers, medical director of the MD Anderson Cancer Prevention Center in Houston, said most women, if they squeeze or stimulate their nipples long enough, will likely see this discharge. "Your body turns over cells and they build up, and you could get some out," she said. If a patient came to see her with this issue, Bevers's first instruction would be to stop squeezing or stimulating the nipple to see if this discharge comes out spontaneously. If so, she says to come back to the doctor and explore any underlying causes.

Brightman said one underlying cause that could produce yellow or green-ish discharge is something called a papilloma, or a benign growth in the duct. These are usually too small to feel during a self-breast exam and are typically diagnosed with the help of an ultrasound or mammogram. The standard treatment is to surgically remove the papilloma and the part of the duct it's in. Bevers said this is a simple outpatient procedure that shouldn't affect your ability to breast-feed.

Yellow or green-ish discharge may also denote an infection if you recently had your nipple pierced. "In any kind of healing process there can be a little bit of discharge," Brightman said. Usually, these infections respond well to topical antibiotics, but in some cases, an oral antibiotic may be required. Either way, any sort of discharge near a piercing site is reason to see a doctor.

If the discharge is clear or white

Obviously, Brightman said, the most common time a woman will see nipple discharge is during pregnancy or while breast-feeding. Colostrum is the first stage of breast milk production, typically shows up during pregnancy, and is usually white-ish in color. But outside of pregnancy and breast-feeding, Brightman said she sees women in her practice who experience white and clear discharge as a result of stimulation.

"If they're running, certain athletes can notice discharge on their jog bra," Brightman said. "That's not concerning, not a bad sign of anything." This liquid is something called "ductal fluid" and, if someone has especially sensitive nipples, can be discharged as a result of a sports bra rubbing during a prolonged bouncy activity like running. Brightman said this is usually fixable with a tighter, more supportive sports bra.

Elevated levels of the hormone prolactin can also cause white or clear discharge, Brightman said. Certain psychiatric medications and some of the medications used to treat the gastrointestinal tract have been known to elevate prolactin levels and result in clear or white nipple discharge. Either way, if this is something you notice, call and schedule an appointment with your doctor.

Discharge and breast cancer

To be totally clear, both Brightman and Bevers said nipple discharge is an incredibly rare sign of breast cancer. But it can and does happen.

Bevers said a doctor might screen for breast cancer if the discharge is spontaneous (meaning it happens without stimulation or squeezing of the nipples), if it's coming from one breast or both (breast cancer almost always shows up in one spot, not multiple), or if the discharge is clear or bloody. A doctor will also ask about family history of cancer and factor that in, too.

 

"The vast majority of nipple discharge that presents like that is due to a benign papilloma," Bevers said. "In a tiny number, it can be due to a breast cancer and it typically is one of the earlier symptoms in those cases." If Bevers suspects cancer could be the underlying cause, she first does a breast exam, then a mammogram, followed by an ultrasound and needle biopsy if necessary. She may also offer to remove the duct producing the discharge entirely — both to put an end to the symptom and rule out the possibility of cancer.

"Spontaneous nipple discharges don't tend to go away on their own." she said. "And most women don't want to live with being in public and a wet spot developing on her shirt. If nothing else, to take care of the symptom, we need to remove [the duct]."

The big takeaways with any and all nipple discharge are that discharge as a result of stimulation is normal. But spontaneous discharge — no matter what color it is — should always be a reason to see your doctor, especially if you aren't pregnant or breast-feeding.