The key word is “discreet,” apparently.

“Tampax Compak has a smooth plastic applicator that is half the length of a usual Tampax Cardboard applicator, making it twice as discreet to carry.”

“New! Neat! Discreet!” proclaims an 80s-tastic ad for Playtex Portables.

“The original o.b. tampon … was revolutionary in the world of tampons and played to women's need for discreet yet reliable protection.”

Tampax Compak is apparently so discreet, according to one old commercial, that a teacher mistakes it for a piece of candy, and asks his student to bring it to the front of the class when he catches her passing it to a friend.

You would think once he held it and felt the hard plastic applicator within the wrapper he would figure it out—tampons and candy bars don’t really have similar tactile sensations. But no. “I hope you brought enough for everyone,” he says, sternly.

“Enough for the girls,” the girl replies, laughing. All the boys in the class look around, confused. This is beyond their simple understanding.

In some sense, they can be forgiven. It’s entirely possible these wide-eyed naïfs have never seen a tampon in the wild, given the sometimes painstaking efforts women make to conceal them (the same efforts that products like Tampax Compak are created to facilitate). You can just palm it, or there’s the ole tampon-up-the-sleeve trick. In sleeveless weather, one can tuck it under the bra strap, or in the waistband. Anywhere tuckable, really. Or just bring your whole purse to the bathroom.

My friend Mallory, a project manager for a digital agency in Nashville, used some creative strategies to carry tampons at her old job. Her office was situated at the end of a long hallway, meaning she had to walk past everyone else to get to the bathroom.

“I would make sure I took care of things in the morning and then always have to remember to take my purse with me to lunch,” she says. “And then one day I was in a bind, I had already gotten up to get coffee and then get water and then I came back to my desk and I realized I hadn’t changed my tampon. It feels too awkward to get up from my desk in the middle of the day and walk out with my purse and then walk back in five minutes later. Then I look at my coffee mug, it was empty. So I stuck a tampon in an empty travel coffee mug and walked to the bathroom. And that was my plan.”

Nadine Ajaka / The Atlantic

Mallory also mentioned a friend of hers with an even sneakier approach—this person apparently hides tampons in the bathroom stalls at her office in the morning, and just hopes they’re still there when she returns.

Why go to all that trouble?

Secrecy is a key element of the modern period—the existence of tampons and pads in the first place allows women to “pass as non-bleeders,” as Sharra Vostral puts it in her book Under Wraps: A History of Menstrual Hygiene Technology. Barring any mishaps, the blood is only visible behind closed doors. Women’s public bathrooms have special trashcans in the stalls so feminine products can be disposed of neatly and privately.

Some of this, surely, comes from the disgust associated with all bodily fluids, and a preference to keep dirty-but-necessary animalistic activities (like excretion) cordoned off by bathroom walls, out of the public eye. But if excretion is a great equalizer (Everybody Poops, as the children’s book says), menstruation divides. Only half the population is biologically predisposed to do it, and the other half would largely prefer not to know about it, thank you very much. Many religions have historically dubbed menstruating women “unclean” and secular shame abounds as well, with jokes aplenty about “that time of the month” and teen magazine “Most Embarrassing Moments” columns filled with period-related anecdotes.

“Menstrual etiquette requires that women hide the fact of their periods…from others, especially from men. Accordingly, they take great pains to keep hygiene products out of sight,” writes Rebecca Ginsburg in her 1996 study “‘Don’t Tell, Dear’: The Material Culture of Tampons and Napkins.”

Pads and tampons themselves often seem designed to be hidden—for one, there’s the plethora of smaller, more “discreet” designs like Tampax Compak and U by Kotex Click,  and a couple years ago Tampax introduced its “Radiant” tampons, which boasted a “softer, quieter wrapper.”

But companies wouldn’t make these products if people didn’t want them. “Incorporating discretion into our products is important because it’s important to our consumers,” Melissa Dennis, the senior brand manager for U by Kotex, told me in an email. “Based on an internal study conducted by Kimberly-Clark [Kotex’s parent company],  95 percent of tampon users reported that tampons are discreet to wear. However, the same study showed fewer tampon users reported tampons were discreet to carry.”

“It’s just one more thing that dudes don’t even realize that we as women have to think about and plan,” Mallory puts it.

In her study, Ginsburg, now director of the Education Justice Project at the University of Illinois at Urbana-Champaign, looked at 150 different packages of feminine hygiene products, and found them generally to be “relatively plain” and to avoid “any reference to the physicality of the objects inside or to their use.” White, pink, and light blue were the most common colors (“Significantly, there was no red on any of the boxes or bags”) and “very few packages contained clear plastic that would allow the consumer to see into the box.” Ginsburg describes this as “the distancing of these products from any suggestion of actual use.”

This was almost 20 years ago, of course. Things are a bit more vibrant than that today in the feminine hygiene aisle, with bright purples, pinks, and yellows (you’d still be hard-pressed to find a red, though) and floral or starburst patterns alongside simpler packages. Still, a more colorful packaging palette doesn’t mean people are eager to put their tampons on display—according to Dennis, in 2014 the compact section of the tampon market grew four times faster than tampons overall.

It’s at least understandable why people are motivated to keep used feminine products concealed—social stigma aside, it’s messy, it’s private—but what’s embarrassing about a clean, unopened tampon? Is it gross by association, like carrying a magazine into the bathroom—everybody knows what you’re going in there to do? Maybe hiding hygiene products is just another way of keeping the poised, public self separate from the animal functions of the body.

Or maybe it’s just savvy self-protection. In one study, people had worse impressions of a woman who dropped a tampon out of her bag than if she dropped something innocuous like a hair clip, and even avoided sitting near her.

Even people who are completely comfortable with their periods might choose to conceal them to avoid that kind of reaction. Efforts to destigmatize menstruation are becoming more mainstream, with even brands getting in on the action with commercials that subvert tampon-ad tropes (like women wearing white spandex and dancing through their periods) or show a girl’s first period as something to be celebrated. “U by Kotex believes that women should not feel like they have to keep the fact that they are menstruating hidden or to have to conceal their products in public if they don’t want to,” Dennis says.

But taboos don’t change that quickly. If there’s a chance open-carrying a tampon in public will only get someone disrespect, maybe she’ll think it’s better to keep it up her sleeve—literally.