An American university has conducted a study of sunscreens that achieve top consumer reviews, and found that the majority do not adhere to The American Academy of Dermatology guidelines on broad spectrum protection and water resistance.

The study, carried out by researchers at the Northwestern University Feinberg School of Medicine, looked at 65 sunscreens that had achieved top customer ratings on Amazon. The study revealed that consumer ratings often focus on the cosmetic aspects of the sunscreens, such as ease of application, absorption and scent, while ignoring effectiveness.

Some 40 percent of the sunscreens investigated by the team did not adhere to AAD guidelines on water resistance, despite carrying product claims to that effect.