Do you need to wear sunscreen only when it is sunny?

That is not the case.

Many people think that they only need to use sunscreen on sunny days, but in fact, this is a misunderstanding. Whether it is sunny or cloudy, ultraviolet rays can penetrate the atmosphere and cause damage to the skin.

One thing you need to know is that ultraviolet rays are mainly divided into two types: UVA and UVB. UVA can penetrate clouds and single-layer glass, causing damage to the skin anytime and anywhere, and is one of the main causes of skin photoaging and increased risk of skin cancer. Although UVB is mainly stronger on sunny days, even on cloudy days, the amount of ultraviolet radiation can reach 80% of that on sunny days.

In addition, ultraviolet rays may also be reflected and scattered from the ground, water and other surfaces to the skin. Therefore, near single-glazed windows or when driving, ultraviolet rays indoors and inside cars may also cause damage to the skin.

As for sunscreen, its main function is to block or absorb ultraviolet rays and reduce their damage to the skin. Therefore, even if it is not sunny, but cloudy or overcast, you need to keep the habit of applying sunscreen. However, the application of sunscreen should be adjusted according to the individual's skin type, activity type and exposure time to ensure adequate protection.

In short, whether it is sunny or cloudy, from the perspective of skin health, it is necessary to apply sunscreen when going out to protect the skin from UV damage. The only difference may be that the UV rays on cloudy days may not be particularly strong, so the sunscreen used does not need to have a very high SPF.

Author: Tang Jiaoqing, MD, attending physician of dermatology

Review | Feng Jun, deputy chief physician of the Dermatology Department of Sinopharm Tongmei General Hospital