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How often should you reapply sunscreen?

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, 5 min read

How often should you reapply sunscreen?

 The importance of sunscreen is often subject to confusion. We’ve all heard that applying sunscreen in the summer is an essential step to avoiding painful sunburns and limiting skin damage. But should sunscreen only be used when the sun is out?

Should you use sunscreen when it’s overcast? Is it only important in the summer or year-round? What does SPF mean, and how should you choose the right SPF for you? Is broad-spectrum sunscreen better?

These questions and more can make sunscreen use more difficult than it needs to be. Make no mistake, using sunscreen regularly is a must for happy, healthy skin. Wearing sunscreen is certainly a good start—one that everyone should embrace no matter their skin type—but it isn’t all that’s necessary to reap the full benefits of sunblock. That’s right; even if you manage to find a comprehensive guide to sunscreen, including the perfect option for your skin, lifestyle, and more, one question tends to persist.

When and how often should you reapply your sunscreen?

SPF and reapplication

To best calculate the frequency with which you should reapply sunscreen, you must have a basic understanding of SPF, what it means, and how it can affect the effective duration of your sunscreen. In other words, SPF is key to sunscreen reapplication.

Sun protection factor—more commonly simplified as SPF—is a way of measuring how well a product protects your skin from ultraviolet rays, specifically UVA and UVB rays.

These UV rays can damage your skin, resulting in sunburn, premature aging of your skin, and even significant health problems like skin cancer. Protecting your skin isn’t just important at the moment; it is vital to your health and well-being long-term.

Contrary to common perception, SPF does not define how powerful sunscreen is or the number of rays it can successfully block. SPF refers to the amount of solar energy (or UV radiation) required to produce a sunburn on protected skin versus the energy required to produce a sunburn on unprotected skin. This can vary depending on the time of day, location, weather, etc.  

These calculations are made under ideal conditions, meaning that variables can diminish a sunscreen’s effectiveness. Peak hours of sun intensity, physical activity, exposure to water, and more can all decrease the duration of sun protection offered by sunscreen, no matter how strong it may be. Still, the SPF ratings on the bottle are a good guide to follow when selecting your sunscreen.

In general, we recommend looking for labels that say "broad spectrum," meaning there is protection provided from UVA and UVB radiation. The amount of sunscreen that should be used per each application is generally 1 oz but may vary on body size and type of sunscreen. Please be sure to read the instructions on the bottle you use.

The skin type factor

Let’s get one thing straight—everyone should use sunscreen. Sun damage can result in age spots, wrinkles, and skin cancer no matter who you are, what your exposure to the sun is, and what skin type you have.

While your skin type is not the end-all-be-all, it does directly influence your risk level and sun sensitivity. Not everyone who shares a similar skin type will share the exact same sensitivity, but there are scales that can give you a general idea of your sunscreen needs.

Speaking to your dermatologist about this particular factor is a great idea, as they can give you a more thorough understanding of how your skin type impacts your sun sensitivity and need for sunscreen. As a general rule, the reapplication timeframe will be similar regardless of skin type, so you can still reapply with confidence.

When to reapply sunscreen the first time

Once you have applied sunscreen—preferably 15 to 30 minutes before sun exposure begins—you will want to reapply multiple times depending on the length of time you plan to spend in the sun. The intervals of sunscreen reapplication are not all the same.

There is a prevailing belief that sunscreen should be reapplied between two and three hours after initial use. While this interval is not technically wrong (more on that in a moment), it is not ideal for a first reapplication.

Research has shown that reapplying around 20 minutes after stepping into the sun maximizes the effectiveness of sunscreen. From there, you should reapply as follows.

Sun protection every two hours

After your initial application of sunscreen, and subsequent reapplication approximately 20 minutes later, you can feel confident in the tried-and-true two-hour rule.

As the name suggests, reapplying every two hours is thought to be the best rule of thumb for effective sun protection. In fact, it’s the most common guidance found on most sunscreen packages, making it a reliable recommendation to follow.

When in doubt, reapply your sunscreen every two hours to keep your skin happy and safe!

Use sunscreen after sweating or swimming

There are a myriad of factors that play a role in how frequently you should reapply sunscreen to maximize skin protection. The type of sunscreen (chemical or physical), SPF level, your skin type, and more are all fantastic examples.

Despite the impressive ability of modern sunscreens to provide protection even when subjected to the elements, one of the most potent factors in reapplication is liquid in the form of sweat or water. This is especially important to remember if you have kids or are being active yourself.

If you have been swimming or sweating, be sure to reapply as soon as you have the opportunity. Sunscreen will inevitably run off, wipe off, and otherwise become less effective under such conditions. Keep in mind that even though some sunscreens may claim to be waterproof, no sunscreen is fully waterproof. 

When in doubt, ask

The tips included here are a great start to maintaining healthy, happy skin year-round. If you would like to learn more about sunscreen, reapplication intervals, and how to best protect your unique skin in your unique life, be sure to have a conversation with a health professional, particularly a dermatologist.

Babylon Health is a superb learning and health care resource for you, no matter what questions or concerns you may have. With exceptional care available 24/7, you can find the help you need with convenience and ease that is revolutionizing the way the world thinks about health care.

The information provided is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Seek the advice of a doctor with any questions you may have regarding a medical condition. Never delay seeking or disregard professional medical advice because of something you have read here.

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