Why some sunscreens turn clothes crimson when bleached

When Clare Mahon went to do her laundry one August day in 2022, she didn’t know it would lead her to uncover a colourful reaction between two common consumer products.

‘I had a white T-shirt that had a sort of greasy-looking stain on it, and I washed it a couple of times and I couldn’t get rid of this stain,’ she recounts. ‘And because it was a white T-shirt, I pegged it out on my washing line and I sprayed it with bleach, and it immediately went bright red!’