Menstrual pads that turn blood solid could reduce the risk of leaks

Menstrual products that cause blood to form a solid gel-like substance, rather than be absorbed, seem to reduce the risk of leaks.

Bryan Hsu at Virginia Tech and his colleagues wanted to find a way of reducing the leaks that often occur with conventional menstrual pads and cups.

They tested various types of biopolymers, naturally occurring chain-like molecules, with pig blood to find one that increases its viscosity. The team used pig blood because it is easier to access than human menstrual blood but has similar properties, says Hsu.

A type of biopolymer called alginate was mixed with glycerol, a sort of alcohol, and then exposed to blood, which created a gel-like substance. “The alginate powder alone, when blood is added, doesn’t absorb the blood very well,” says Hsu. “It has kind of like an unstirred-cocoa-powder-in-milk consistency with a dry core. We added the glycerol to the alginate to improve its ability to absorb blood.”

To put the combination to the test, the researchers added 8 millilitres of blood to an artificial vagina, simulating a period. They made this bleed onto a standard menstrual pad where the internal absorptive material had been removed and replaced with gauze coated in the alginate-glycerol mixture. One hour later, this pad had retained more blood than when the vagina bled on standard pads that hadn’t been altered.

In another part of the experiment, five people removed menstrual cups filled with blood from the synthetic vagina but were blinded to whether they were lined with the alginate-glycerol mixture or not. The former led to almost no spillage, whereas the latter consistently resulted in spills.

Alginate is naturally found in algae and is sometimes used in wound dressings. “Alginate likes to form intermolecular cross-links by using calcium, and blood has calcium,” says Hsu. “We think these polymers initially absorb the blood, and as they dissolve, they start to form these cross-links, which eventually gels the blood.”

Renske van Lonkhuijzen at Wageningen University & Research in the Netherlands says adding this mixture to menstrual products could make women less anxious about blood leaking while they are on their period.

“Innovative products can improve menstrual comfort and convenience, making it easier for women to manage their periods without disruption to their daily lives,” she says.