Paris - The US firm Procter and Gamble has filed patents for sanitary towels that will advise women when they are pregnant, about to ovulate or have their period, or if they have HIV or thrush.
The worldwide patents include smart pantyliners that are impregnated with guam guaiac wood resin, which turns blue in the presence of blood, and a sensor that turns blue in the presence of acidity.
These markers turn purple four hours ahead of menstruation, giving the wearer plenty of notice, the British weekly New Scientist reports.