Moshi, Tanzania — Every month when payday came around, Suzana Frederick purchased a packet of sanitary pads. It was the first thing she bought. And when her period started, she knew she was ready for it.

The 19-year-old single mother from Arusha, Tanzania, was making 30,000 shillings ($13) a month as a housekeeper and would spend between 1,500 and 3,000 shillings ($0.70 to $1.30) on pads -- a staggering 5% to 10% of her salary.

For an American woman making a typical wage, that would be the equivalent of between $169 and $338 for just one pack of sanitary pads.

The steep price was worth it for Frederick. The alternative of missing a few days of work each month to manage her period at home would have been more costly.

Roughly 1.8 billion people around the world menstruate. Some can't afford sanitary products. Others have nowhere to buy them. And even if price isn't an issue, stigma and taboo still stop many from fully participating in work and school during their periods.

For these women, the cost of menstruation is missing out on life.

Girls use fabric and rugs, but dream of pads

In rural Tanzania, most women and girls on their period use "kanga," layered pieces of thick, colorful fabric used for making traditional east African dresses.

The stiff material gets wet quickly and often leads to urinary tract infections. Girls and women say they live in constant fear of bleeding through.

"I put [it] on in the morning, it will be wet with blood at 10 a.m. and start showing on my skirt," says Esuvati Tisanai Shaushi, a 15-year-old Maasai girl who lives in a village near Arusha. Her school, like many in Tanzania, doesn't have toilets with running water to wash.

"I feel ashamed... [I] keep on wondering how it will be [what will happen] in class."

Among young girls in Tanzania, the gold standard of sanitary pads is Procter & Gamble's brand Always.

Tisanai Shaushi has used them only once, when she was given a sample at school.

"I was so happy," she said. "When I removed it, my pants were clean. It was comfortable."

But when she asked her mother to buy the pads for her, the answer was no.

"She told me to use kanga because she uses them too," Tisanai Shaushi said. When she pressed the issue, her mother told her she could buy them when she got her own money.

Procter and Gamble (P&G) has invested heavily in educational campaigns in East Africa, including in Tanzania. Among other initiatives, it provides samples and starter packs to schools. But once the samples run out, the girls often go back to using kanga. Always pads are not widely available, and when they are they're more expensive than other products.

Jennifer Davis, the global head of feminine care at P&G, told CNN the cost reflects the quality: "The foundation of our portfolio globally is always superior protection."

P&G doesn't break down its revenues from its different products. But Euromonitor International, a market research company, estimated P&G made $6.2 billion selling feminine care products in 2017 -- more than any other company.

Davis declined to say how much P&G makes per pack, but said it is trying to keep pads as affordable as possible.

However, Always pads remain unaffordable for many Tanzanian girls.

Jennifer Rubli from Femme International , a menstrual health NGO in Tanzania, says P&G has done a great job marketing its products.

"Girls don't talk about wanting disposable pads. They want Always," Rubli said.

Other cheaper sanitary products are available in Tanzania, but the selection is limited.

Chinese-made pads -- perfumed with menthol and aloe vera "flavors" -- are typically slightly less expensive and more widely available in Tanzania, but several women and girls who spoke with CNN complained of "burning" and "itching."

"I used pads only once, and I felt a burning sensation. After using it for six hours and changing it, I was burning," one woman, Yuster Venance Kimaryo, a 37-year-old fruit trader in Moshi said. "That's when I stopped using it."

Period absenteeism

There are no global statistics on how many girls miss school because of their periods, but anecdotal evidence shows that period absenteeism is common across much of the developing world.

In Tanzania, 16% of girls say their periods keep them out of school, research by the Tanzania Water and Sanitation Network found.

During a recent school day, Violeth Hugolin Msophe, a pupil at Ghona Secondary School in Moshi, near Kilimanjaro, bled through her kanga and all over her dark green skirt. She wrapped her sweater tightly around her waist, asked a teacher for permission to leave and walked two hours home.

Martha Msangi Goodwine, the teacher who's in charge of girls' welfare at the school, said this happens so often that teachers sometimes buy pads just to have them on hand -- but they can't afford to supply the whole school.

"Many children here come from villages and very few are able to buy pads in the shops," she said.

When non-profit organization Femme International gave each girl at Ghona a pack of AFRIpads -- reusable pads that last as long as eight hours and are effective for up to a year -- it was a game changer, especially for girls from poorer backgrounds who were using old rugs as pads.

"Most of them suffered from infections and other diseases, all that because of those rugs," Goodwine said.

Girls are suffering fewer illnesses since using AFRIpads, made from absorbent, quick-drying fabric, that secures to underwear with snaps, Goodwine said. The school's headmaster Peter Mushi said attendance has improved after the girls got AFRIpads. He doesn't have precise figures, but said the effect was "noticeable."

Speaking about the pads, Sophia Grinvalds, who co-founded the company with her husband in 2010, said "the onset of puberty should not simultaneously mark the end of schooling or a monthly experience of indignity and shame and stigma."

Grinvalds said the idea for reliable reusable pads came from her own experience living in a village in Uganda. While washing sanitary pads might be unusual in developed countries, it is not a barrier in poor communities, where women routinely use and wash pieces of cloth.

AFRIpads has already made 2.5 million pads. The company is building a new factory that will make it possible to increase production three-fold.

It's not only access to pads that keeps girls out of school it's also period pain and untreated conditions.

Tisanai Shaushi says the beginning of her cycle is too painful to walk the short distance from her village to school; she often misses one or two days every month. She's never taken any pain medication. Like sanitary pads, they are out of reach for her.

"There are periods when I am in school and I cannot write because of the pains," Tisanai Shaushi said.

Tisanai Shaushi wants to be an engineer one day. But to do that, she needs to get good grades and win a place in one of the few high schools in her area. By keeping her out of school every month, Tisanai Shaushi's period is another barrier she has to overcome.

"I keep on asking myself why does it have to be that way," she said.

Menstrual pain is poorly understood, even in the world's richest countries. Long-term conditions like endometriosis, which affects one in 10 women of reproductive age, are often misdiagnosed and go untreated. But in the developing world, pain isn't just misunderstood, it's ignored.

"[Girls] are leaving [school] early because of it, or they're not concentrating, so even if they are staying in school and being marked present ... they're not taking anything in," Rubli said.

Tisanai Shaushi is worried about falling behind. And she's not alone -- three-quarters of Tanzanian girls say their periods affect their performance in class, according to the Water and Sanitation Network.

While primary school enrollment among girls and boys is nearly equivalent in Tanzania, that changes in secondary school when puberty hits.

Nearly 61% of girls of secondary school age are out of school compared to 51% of boys, according to the 2014 Demographic and Health Survey, a program funded by the U.S. Agency for International Development.

A 2018 study by Unicef and Unesco found girls are more likely to be out of school in Tanzania starting aged 15 and increasingly so as they get older.

The real price of periods

Elizabeth Scharpf was working for the World Bank in Mozambique when she saw the economic cost of menstruation first hand at a struggling factory making computer bags.

"The head of the factory told me that the female workers miss two to three days of work a month when they are menstruating," she said. A quick calculation revealed the business was losing 20% of its workforce because women could not afford menstrual pads -- and profits were taking a hit.

In response, Scharpf started Sustainable Health Enterprises (SHE), a social venture aimed at addressing period poverty.

Researchers, NGOs and charities all agree that it makes economic sense to start taking periods seriously.

"Whether directly or indirectly, [menstruation] actually affects everybody...and yet people who menstruate are unduly punished, because of something that's completely normal and natural," Femme International's Rubli said.

Tanzania's government reports that 60% of women live in "absolute poverty."

The period poverty situation in some cases is so extreme that research conducted by nongovernmental organizations found that women engaged in transactional sex to obtain pads.

"As a woman you're already economically disadvantaged to begin with and you're put in this position where you have to fight that much harder the rest of your life because of something that you had no control over,' Rubli said.

Suzana Frederik has been through a lot. Her mother died when she was very young. When she was in fifth grade, she lost her father.

Primary education is free in Tanzania, but compulsory uniform, school shoes and equipment became prohibitively expensive for Frederik. She dropped out shortly after her father died.

When she got pregnant aged 17, her boyfriend told her to get abortion. She refused and ended up alone, with a child to feed.

Spending 2,000 shillings ($0.87) on a pack of pads meant less money to buy food for the two of them.

She said she was lucky. "My periods lasts for three days, so one pack is enough for me."

Frederick, who now lives in a shelter for vulnerable women, can get pads when she needs them. But access to pads is still out of reach for millions of women around the world.