How Bad Is It Really to Wear an Underwire Bra?

News flash: Underwire is over. An August 2019 report from the market research group NPD confirms that comfort is the number-one thing shoppers look for in a bra.

According to the report, sales of sports bras have exploded, with people assigned female at birth (AFAB) keeping them on all day long instead of just while exercising. Meanwhile, brands specializing in wireless support — like LIVELY, Knix and Pansy — are popping up left and right.

While lots of people AFAB are turning to soft cups for the loungy feel when WFH, some are also concerned that underwire might be bad for you — primarily, that this type of bra might cause breast cancer.

Here, we investigate whether how you cradle your twins has any bearing on your health.

For decades, there have been rumors about a link between underwire and breast cancer. The theory is that underwire might block the flow of lymph fluid, so toxins aren't adequately flushed out and instead build up in the body, leading to cancer.

To understand what's behind this idea, let's start by looking at how the lymphatic system works.

"The lymphatic system is made up of lymphatic vessels — which are similar to blood vessels — lymphatic fluid and lymph nodes," says Deanna Attai, MD, associate clinical professor of surgery and member of the UCLA Jonsson Comprehensive Cancer Center. "Lymphatic fluid circulates through the lymphatic vessels and is rich in an immune cell known as a lymphocyte, which is important in the body's response to bacteria and viruses. Lymph nodes, which are present throughout the body, serve as filters for lymphatic fluid."

In addition, the lymphatic system maintains fluid levels in your body and transports nutrients from the intestines to your bloodstream, according to the Cleveland Clinic.

"The lymphatic channels are also where the body gets rid of bacteria, viruses and even cancer cells," says Marisa Weiss, MD, founder and chief medical officer of Breastcancer.org. "The lymph nodes in your armpit filter out this 'trash' — similar to how the filter basket covering a sink drain catches hair and debris to stop it from going down the pipe. Then, your immune system attacks anything in the lymph nodes that's not supposed to be there."

So, could a bra with a rigid, tight underwire obstruct the critical passage of fluid to the lymph nodes?

"People are concerned that the lymphatic fluid could get stuck in the breast," Dr. Weiss says. "And if your body is marinating in unhealthy fluid that contains abnormal cells or waste products, then over time it might pollute the breast and cause problems like cancer."

It sounds plausible. After all: "Underarm lymph nodes may be the first place that breast cancer spreads," Dr. Attai says.

But you can breathe a sigh of relief: "The fact is that the lymphatic fluid remains in circulation, even when you are wearing clothes that put pressure against the lymphatic channels," Dr. Weiss says.

In fact, a September 2014 study in ​Cancer Epidemiology, Biomarkers and Prevention​ determined that no aspect of bra wearing — including cup size, number of hours per day worn, and, yes, whether or not the bra had an underwire — was associated with an increased cancer risk.

Got a milk vampire on your hands? Many lactation consultants say it's best to skip the underwire.

"My recommendation is not to wear a bra with underwire as they can put significant pressure on the milk ducts and cause plugging, which can lead to mastitis," says Mary Lou Judas, IBCLC, registered nurse and lactation consultant at Dartmouth-Hitchcock Medical Center. "This in turn can decrease milk supply."

Mastitis can also cause pain, swelling, flu-like symptoms and possibly an infection, according to La Leche League International.

"Breasts change a lot as milk comes in, so often the wires — or even tight elastic — can shift and be on the breast tissue itself instead of supporting from behind," Judas says. "There are many supportive bras available without wires, and fit is actually the most important thing."

So do a self-check on your rack pack: "Raise your arms up and move them around to see if the bra is comfortable," says registered nurse and lactation consultant Andrea Tran, IBCLC, founder of Breastfeeding Confidential. "Make sure it does not ride up, shift or put pressure on the breast tissue."

While we're at it, BF parents should also steer clear of wearing super snug sports bras, aside from during workouts. "If a bra constantly compresses breast tissue where there are milk-producing glands, that can destroy the milk-producing cells and diminish supply," Tran says.

Pack your underwire away if you're nursing. Otherwise, you're in the clear.

"There is no scientific evidence that underwire bras cause cancer," Dr. Attai says. "If a woman is comfortable in an underwire bra, I am not aware of any downside to it."