Photonic crystals are periodic optical structures that can control the flow of light. Multiple reflections from surfaces separated by a distance similar to the wavelength prevent an optical beam ...

Delyth Morgan, of Breakthrough Breast Cancer, said: "This extremely small study does not demonstrate a direct causal link between deodorant or anti-perspirant use and developing breast cancer.

What to know before using whole-body deodorant. (Getty Images) ...

Only the formulas that passed our 24-hour sweat test made this list.