It has clearly worked on DS aged 3. he is obsessed with Vanish (we've never bought it) and is desperate for us to get some. If he spills food on himself, he suggests we buy some to get rid of the stains.
You'd think a child who threw a pizza in the air and let it land on his trousers would get a telling off, not a demonstration of a stain remover from a passing stranger. How does that woman just waltz into people's houses anyway? Do none of them lock their door? She must be hanging around outside, peering through the windows, waiting for stains to happen. Weirdo.