Over the years, advertisers of sanitary protection have tried, repeatedly, to convince us that a woman's period is a glorious time. A hallowed time. A time to ice skate, bungee jump and rollerblade. A time to leak blue liquid and listen to soft rock. And a time when we feel compelled to wear our tightest, whitest shorts.

Such ads obviously do nothing to prepare girls for the painful reality, so it's interesting to see a different approach. Over the past few months, a viral campaign has been running online - complete with blog, videos and Twitter feed - which features no bungee jumping at all. It also stars a man. Well, a 16-year-old boy anyway. And one day said boy, Zack, wakes up with a vagina.

The campaign follows his struggle to cope. In some ways, it pops with sexist stereotypes: he starts baking brownies, eating yoghurt and snapping at his best friend, Bryan. Overall though, the story unfolds skilfully, exploring what it's really like to have your first period, including the shock of cramps and water retention. Zack invites commenters to write about when they had their first period, opening up a public discussion that's rarely mooted. And it's only towards the end of the video sequence that he's shown using a Tampax slot machine.

The campaign is intriguing partly because it's so difficult to tell who Tampax is targeting. Is it young women in general? (Zack is good looking.) Is it female athletes? (As a footballer, Zack asks sporty women how they cope with their periods.) Or could it be men? Are they the secret, untapped market for sanitary products? Would Tampax sales shoot up if they could convince bashful blokes to buy tampons for their girlfriends? So many questions.