A TV ad by underwear brand Wuka will continue to air despite it racking up 295 complaints to the Advertising Standards Authority.
The taboo-breaking ad, which demonstrates Wuka's leakproof range of reusable underwear, includes blood clots and period bleeding in the shower.
The complainants contacted the ad regulator to argue the imagery is offensive and likely to cause distress.
In reaction, Wuka argued it pro-actively represented periods positively in the hope of encouraging people to talk more openly.
For Wuka, graphically depicting "real" periods helps normalise attitudes and perceptions.
It claimed period clots are a common symptom of menstruation, and underscored it followed medical guidance about the size and colour to ensure it was depicted accurately.
Further, Clearcast cleared the ad with an "ex-kids" scheduling restriction.
After consideration, the ASA decided not to ban the ad. Firstly, it said it was clear from the beginning it was related to menstruation, and therefore likely to feature imagery related to periods.
Given the context of the ad, the ASA said blood and blood clots would be recognised as menstrual flow, but it admitted this imagery was less common in the period ad category.
Although some of the blood imagery was associated with injury, which the ASA acknowledged might be distressing for viewers, in the context of the period product, it was a realistic and accurate depiction of consumers' menstruation experiences.
And while some young children might find the imagery unfamiliar, the average menstruation age begins at 12, with children starting their period as young as eight.
While the ASA admits some viewers might find the content distasteful, it concluded: "The imagery was not likely to cause serious or widespread offence, or excessive fear or distress."
In 2017 Bodyform and sister brand Libresse produced the first ad – “Blood normal” – to depict real menstrual blood instead of blue liquid.