Stroll down the menstrual products aisle of your neighborhood drugstore, and you'll see a dizzying array of disposable pads and tampons in dozens of brands, shapes, colors and sizes.

Tucked away on one of the shelves, you might see a lesser-known option: the reusable menstrual cup.

It's a bell-shaped container, made of silicone, latex or rubber. Like a tampon, it's inserted into the vagina when people have their period. But instead of absorbing menstrual flow with cotton, the cup collects the flow in its receptacle, which stays in place around the cervix through the power of suction (more on that later). And it can be used for up to 12 hours before being emptied. The cup isn't cheap — the Diva Cup, for example, which sells at CVS, costs about $40. But the lifespan is about10 years.

Although the menstrual cup has been around for decades — some early commercial models date back to the 1930s — it's not as popular as pads and tampons. The device has had a reputation for causing possible health problems and being uncomfortable. And for religious and cultural reasons, some believe that it is inappropriate.

A comprehensive new analysis published in The Lancet Public Healthon Tuesday could help change that narrative. The report finds that menstrual cups are safe to use and may be just as effective as other sanitary products in preventing leaks. The paper shows that the cup could be a viable option in poor countries, where access to menstrual products might be limited and costly in remote areas.

"People say that they are not safe, they are taboo, that women aren't going to use it because it's invasive and not culturally accepted," says Penelope Phillips-Howard of the Liverpool School of Tropical Medicine, the report's senior author. "We are able to put to rest some of those concerns."

The researchers looked at 43 studies on menstrual cup use globally, which included data from 3,319 women and girls.

Probably one of the most important findings, says Chris Bobel, an associate professor of women's, gender and sexuality studies at the University of Massachusetts, Boston, is that menstrual cups are just as good at preventing period leaks as pads and tampons. One study even found that menstrual cups had significantly less leakage. Bobel did not take part in the Lancet study.

"That's pretty exciting to hear because a lot of people are nervous about using cups," says Bobel, the author of The Managed Body: Developing Girls and Menstrual Health in the Global South. "Leaking is like social suicide. People don't want the embarrassment of having a menstrual stain on their clothes. Or the discomfort of it."

In terms of health, the researchers found no increased health risks associated with menstrual cup use among European, North American and African women and girls. In four studies involving 507 women, menstrual cups did not have negative effects on the vaginal flora — the bacteria that live inside the vagina — that could lead to infections or vaginal discharge.

Because the device has to be inserted into the vagina, there has been a long-standing concern that menstrual cups cause toxic shock syndrome (TSS). The researchers found that in the study sample, there were only five reported cases of TSS, a potentially fatal condition caused by the bacteria Staphylococcus aureus. But the researchers were not able to compare the risk of TSS from menstrual cups with the risk from other products because the overall number of menstrual cup users is not known.

Bobel believes that the paper has groundbreaking implications for the booming number of nonprofits and organizations working to address menstrual health in low- and middle-income countries. "This body of research is important because so many organizations are promoting menstrual products in schools and other settings [in the developing world] and cups have to be an option," she says.

Advocates in the global menstrual health community have not traditionally promotedmenstrual cups in low-income settings, says Mandu Reid, founder of The Cup Effect, a group that trains people how to use menstrual cups in the U.K., Kenya and Malawi.

"People in [nonprofits] assume that [the cups are] not suitable," she says. "That's based on presumptions about these women's preferences. That they wouldn't like them because they have to be inserted or because they don't want to touch their own menstrual blood."

The study, however, finds that many of the people who give menstrual cups a try actually like them. Of the participants, 73% of women and girls reported a willingness to continue with the menstrual cup after learning how to use it and trying it out for several menstrual cycles.

"Menstrual cups can be difficult to use — I thought that at first," says Reid. "It seemed like the most clumsy, awkward thing ever. But then when it was explained to me, I found it more convenient."

Indeed, it can be tricky to put in a menstrual cup. First, you must fold up the cup (and there are lots of different ways to do this) so that the bell-shaped opening can be inserted into the vagina. Once it's in, the user rotates the cup 360 degrees so that it reopens. The cup will then form a seal by suctioning around the cervix.

Over the next few hours, you can do pretty much anything: run, swim, do yoga and yes, even pee (that comes out of a different hole). Depending on the user's flow, the cup must be emptied every four to 12 hours. To remove, wash your hands with soap and clean water. Reach in and pinch the base of the cup to release the seal. Carefully pull the cup down and out of the vagina. Pour the menstrual blood into the toilet, rinse the cup out with clean water and reinsert.

At the end of the menstrual cycle, users should thoroughly wash and dry the cup, then store it in a breathable container (many commercial menstrual cups come with cloth satchels).

It's a lot to learn. That's why instructional efforts — like the ones run by The Cup Effect — are key, says Phillips-Howard. "You can't just throw cups at girls. You need to train people to use it properly so that they feel comfortable and confident to insert it. And they need a number of trainings to make sure they are using it correctly."

The study also provides evidence that menstrual cups can be used in challenging environments. "Some people said that it would be unsafe to use them [in low- and middle-income countries] because of lack of water and sanitation," says Phillips-Howard. "Well, our study didn't pick up on that at all."

In one pilot study of schoolgirls in rural Kenya, for example, the researchers found there was no difference in the prevalence of infections among girls who used menstrual cups, sanitary pads or cloths, or other makeshift materials.

"Even in situations where there was less water available, like in refugee camps, [people] figured out how to [clean] menstrual cups with less water," says Phillips-Howard.

In two studies, the researchers found that menstrual cups actually reduced the amount of water that people needed to manage their periods. Less leakage means that people didn't need to wash stained clothing as much. And women who use cloth as a reusable pad also need a supply of water for washing.

As for the cost factor, the researchers found that the average global price of a cup is $23 — a lot of money in a poor country. But over time, the cup is a tremendous money saver. The cost of a cup represents only 5% of the cost of a 10-year supply of pads or tampons.

Menstrual cup companies like , which sells the device commercially in Europe, are trying out ways to make cups affordable to girls in countries across sub-Saharan Africa.

Julie Weigaard Kjær, founder of Ruby Cup, says the company looked at a number of approaches: having girls pay for the menstrual cup in installments or having women buy the cups in bulk and sell them to their friends, similar to Tupperware parties. The company settled on a "buy one, give one" approach. For every cup sold in Europe, Ruby Cup donates one to a girl or woman supported by its program.

But there's a cautionary note. Phillips-Howard wants people to know that menstrual cups aren't for everyone.

"Everyone's physiology and anatomy is different. There will be people who will try it and they just can't use it," she says. It might not fit, or it might cause pain. There's also the ick factor. "Some people — they just don't like it."

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