LONDON: In total, women spend around six to seven years of their lives menstruating.
For women and girls to live healthy, productive and dignified lives, they must have access to toilets, water, soap and sanitary towels, development experts say.
Yet too often their needs are being neglected, experts say.
Menstrual Hygiene Day, which aims to raise awareness about the issue, takes place on May 28. Below are some questions and answers about menstrual hygiene and why it is important.
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Why does menstrual hygiene matter?
On any given day more than 800 million women between 15 and 49 have their period.
However, globally 1.25 billion women do not have access to a toilet during menstruation, according to the charity WaterAid.
The United Nations estimates that due to a lack of facilities, one in 10 girls in Africa will miss school during their period and will eventually drop out of school as a result.
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Where is menstruation still a taboo?
Menstruation is still taboo in many countries around the world. Women refer to periods using some 5,000 euphemisms, such as "on the rag" and "Bloody Mary", a survey of 90,000 people in 190 countries found.
In parts of Nepal, women practice "chaupadi", a tradition which cuts them off from the rest of society when they are menstruating. The custom obliges women to sleep in sheds or outbuildings while they are on their period.
They are not allowed to enter houses or temples, use public water sources, take part in festivals or touch others during their menstruation.
Despite being outlawed by Nepal's supreme court in 2005, "chaupadi" is still practised by as many as 95 percent of girls and women, says grassroots organisation Action Works Nepal.
Almost half of girls in Iran and 10 percent of girls in India believe menstruation is a disease, according to WaterAid.
Discrimination against menstruating women is also found in parts of Africa.
"In Sierra Leone, for example, some women are forbidden from entering religious ceremonies and key community engagements during their period as they're seen to be tainted in some way," Apollos Nwafor, WaterAid's West Africa advocacy manager, told the Thomson Reuters Foundation.
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Why is it a neglected issue?
In total, women spend around six to seven years of their lives menstruating yet their needs are often overlooked by those responsible for ensuring access to water, sanitation and hygiene.
Lack of awareness about the problem and appropriate solutions among often male policymakers and male-dominated communities means that menstrual hygiene is not prioritised, researchers say.
What are some of the impacts?
Social exclusion, shame and embarrassment.
"If girls get blood on their skirts when they are on their periods, the boys would say, 'shameless girls'. They would disgrace and tease us," WaterAid quoted Ayisha Sadik, a high school student in Ghana's East Gonja district, as saying.
"You feel uncomfortable because boys have seen blood on you, and you would be panicked in class. Even to play with them, it is very difficult."