Sanitary napkins with blood-thinning properties could prevent leaks

Sanitary products that turn blood into a gel-like solid substance rather than absorbing it appear to reduce the risk of leakage.

Brian Hsu Researchers at Virginia Tech and their colleagues wanted to find a way to reduce the leakage that often occurs with traditional sanitary napkins and cups.

The team tested different types of biopolymers — naturally occurring chain-like molecules — in pig blood to find one that would thicken it. They used pig blood because it is more readily available than human menstrual blood and has similar properties, Xu said.

When a type of biopolymer called alginate was mixed with glycerol, a type of alcohol, and exposed to blood, it formed a gel-like substance. “If you just take alginate powder and add blood, it doesn't absorb much,” Su says. “It becomes like cocoa powder in unstirred milk, with a dry center. By adding glycerol to the alginate, we've increased its blood absorption capacity.”

To test the combination, the researchers placed 8 milliliters of blood into an artificial vagina to mimic a period, then let the blood flow onto a standard sanitary napkin that had had its absorbent material removed and replaced with gauze coated with a mixture of alginate and glycerol. After an hour, the napkin had collected more blood than vaginal bleeding from a standard, unmodified napkin.

In another part of the experiment, five subjects removed a blood-filled menstrual cup from the artificial vagina without knowing whether the cup was covered in the glycerol-alginate mixture. In the former case, blood rarely spilled, whereas in the latter case, blood always spilled.

Alginates are found naturally in algae and are sometimes used as wound dressings. “Alginates are good at forming intermolecular cross-links using calcium, and blood contains calcium,” says Su. “We think these polymers first absorb the blood, and as they dissolve they start to form cross-links, eventually gelling the blood.”

Renske van Ronkhuizen Researchers from Wageningen University in the Netherlands say adding the mixture to sanitary products could help reduce women's anxiety about bleeding during their period.

“The innovative products improve menstrual comfort and convenience, helping women to manage their periods without disrupting their daily lives,” she said.