Do you need to reapply sunscreen every 2 hours because it stops working? Know truth about how often you actually need it

When do your 2 hours start?

In a November 25 Instagram video, Skin Ritual explained that the standard two-hour countdown only starts when the skin is actively exposed to the sun. The time limit exists because UV rays chemically break down the sunscreen’s protective barrier over approximately two hours of use. According to Skin Ritual, remaining indoors largely pauses the protective countdown.

According to Skin Ritual, “Sunscreen doesn’t just stop working after 2 hours of time. It actually stops working after 2 hours of actual sun exposure. And the two are not necessarily the same. If you put your sunscreen on at 9am and then you stay indoors until 12pm. Once you go outside at midday, that’s when your 2 hours starts.”

In office, should you be reapplying every 2 hours?

Skin Ritual suggested that for individuals working in an office or building with minimal UV exposure, reapplication every two hours is generally unnecessary: “So, up until then, you haven’t used up any of the protection that your sunscreen provides because you weren’t actually exposed to UV. The reason that sunscreen even has a time limit on its effectiveness is because UV rays actually break down your sunscreen, which ultimately means it stops working. The process of UV breakdown of sunscreen takes roughly 2 hours and that’s why we say reapply every 2 hours of sun exposure. Often people ask me, do I need to reapply all day long? If I’m in the office, should I still be reapplying every 2 hours? The answer is almost definitely no because you’re not actually getting sun exposure.”

Skin Ritual stressed that external factors can instantly shorten the duration of protection. Heavy sweating, water immersion, or physically rubbing the face will necessitate much sooner reapplication, regardless of UV exposure time.

“And I will add a caveat to this. Obviously, sweating and water exposure and rubbing your face are all going to affect your sun protection. So, if you had an hour of sun exposure, but you were sweating heavily or rubbing your face with a towel, you probably don’t have an extra hour in that sunscreen. So, if you’re using a sweat resistant or water resistant sunscreen, usually they’re rated for 80 minutes. So, at that point, you would reapply. Like everything skincare related, of course, it’s case by case. There are caveats, but essentially understanding that it’s UV that breaks down your sunscreen and not just the passage of time on its own gives you a better understanding of when you actually need to reapply,” Skin Ritual concluded.

‘Use sunscreen with at least SPF 30 to 50’

When asked about these claims, Dr Shareefa Chause, dermatologist at Dr Shareefa Skin Care Clinic in Mumbai, reinforced the importance of a consistent reapplication routine, especially for those spending time outdoors. Dr Chause noted that the protective layer typically begins to break down after about 3 to 4 hours of sun exposure due to a combination of factors, including sweating, rubbing, and UV rays. In an interview with HT Lifestyle, she strongly advised against the belief that a single morning application is sufficient.

She said: “Many people believe that applying sunscreen once in the morning is enough, as doing so tends to protect their skin throughout the day. But you have to keep reapplying the sunscreen without fail. Typically, after about 3 to 4 hours of sun exposure, the protective layer starts to break down due to factors like sweating, swimming, rubbing, or even natural breakdown from UV rays. This means that even if you applied sunscreen properly in the morning, by midday, you need to reapply it again for skin protection from those harsh UV rays. Understand that sunscreen is like an invisible shield for your skin, but like any shield, it can wear off. Hence, reapplying after every 3-4 hours can help to prevent sunburn and reduce long-term risks like premature aging and skin cancer.”

She added: “People should also use a broad-spectrum sunscreen with at least SPF 30 to 50, and make sure to cover all exposed areas, including ears, neck, and hands. Remember, it’s not about applying sunscreen once and forgetting it; it’s about maintaining a routine that keeps your skin safe throughout the day.”

While Skin Ritual’s guidance focused on UV exposure as the trigger for breakdown, Dr Chause said that sunscreen also plays a protective role indoors and that reapplication is a necessary habit: “It is a myth that if you are not exposing yourself to the sun, you don’t need sunscreen. Apply sunscreen even when you are indoors and reapply once you step out of the house, too. Note that the effect of the sunscreen doesn’t start only when you expose yourself to the sun. It also does the protection work even when you are indoors. Keep re-applying the sunscreen as advised by the doctor.”

The overall consensus from both the skincare creator and the dermatologist is that while the mechanism of breakdown is chemical, maintaining a regular, vigilant routine is essential for optimal skin protection, especially when active or outdoors.

Note to readers: This report is based on user-generated content from social media. HT.com has not independently verified the claims and does not endorse them.

This article is for informational purposes only and not a substitute for professional medical advice.