Here’s How Often You Should Reapply Sunscreen, Say Dermatologists

Skin cancer remains the most common type of cancer in the United States, according to the American Cancer Society. While melanoma accounts for only a fraction of skin cancer cases, it causes the majority of deaths related to the disease. In 2024, it’s estimated that around 100,640 new cases of melanoma will be diagnosed, and approximately 8,290 people will die from it.

These statistics serve as a crucial wake-up call about the importance of proper skin care. You probably already know sunscreen is a crucial part of maintaining your skin’s health and preventing cancer, but there are clear recommendations from skin health experts and consistent research about how often sunscreen needs to be reapplied.

The reason you need sunscreen at all starts with this: When human skin is exposed to ultraviolet (UV) light, these rays can damage the DNA inside skin cells. Both chemical and mineral sunscreen formulas work by absorbing UV light and converting that energy into small amounts of heat.

To set the stage for how often to reapply sunscreen, Susan Y. Chon, MD, dermatologist and assistant professor at the University of Texas MD Anderson Cancer Center’s department of dermatology, points out: “Most people don’t apply enough sunscreen.” To ensure that your sunscreen is working, it’s essential to apply a sufficient amount and reapply it often, which Dr. Chon says “can greatly curb your chances for sunburns and skin cancer.”

Ahead, we share instructions from dermatologists related to how often you should reapply sunscreen.

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Here’s how often you should reapply sunscreen, a dermatologist says

As a general rule, you should reapply sunscreen every two hours.

This timeframe can vary depending on your activities and exposure conditions. Dr. Chon says if you’re using a spray sunscreen, or if you’re swimming or sweating, you must reapply every 60 to 90 minutes. Water, snow, and sand can intensify the sun’s rays, leading to a greater risk of sunburn, so make sure to take extra precautions in these environments.

It’s also important to remember that your skin can take up to 30 minutes to absorb sunscreen fully, so be sure to apply it at least half an hour before heading outdoors.

Here’s how long sunscreen lasts on skin, dermatology experts say

Sunscreen typically lasts only two hours on your skin, the American Academy of Dermatology (AAD) states. This is the case even though many sunscreens are marketed to provide “all-day protection.”

However, how long your sunscreen remains effective is typically influenced by several factors: For example, if you’re swimming or sweating heavily, your sunscreen can wash off or break down more quickly, requiring more frequent reapplication.

The type of sunscreen formula you use also plays a role—water-resistant varieties offer longer-lasting protection under wet conditions than regular formulas.

Ultimately, as Johns Hopkins dermatologist Anna Lien-Lun Chien, MD, states, “The best sunscreen is the one you’ll reach for every day.”

To ensure that you’re choosing a sunscreen that provides the best possible protection, the AAD recommends looking for products with the following features:

• Broad-spectrum protection
• SPF 30 or higher
• Water resistance

Your lips are also susceptible to sun damage and skin cancer, so apply a lip balm or lipstick that contains sunscreen with an SPF of 30 or higher.

How much sunscreen should I use when reapplying?

When reapplying sunscreen, ensure you use the same amount as your initial application—about one ounce, roughly the amount needed to fill a shot glass. This should equate to two milligrams of sunscreen per square centimeter of skin.

Dr. Chon advises not to overlook any exposed skin, including often-forgotten areas such as the ears, the back of the neck, and the tops of the feet. Apply an even layer across all these areas, ensuring no patches are missed to maintain the best possible protection.

What happens if I don’t reapply sunscreen?

If you don’t reapply sunscreen, your skin becomes more vulnerable to UV damage. This accelerates skin aging (wrinkles and sunspots) and increases your risk of developing skin cancer.

The cumulative effects of sporadic sunscreen use can lead to significant skin damage. Each instance of sunburn or tanning increases the likelihood of malignant changes in skin cells. Sunscreen isn’t just about preventing a painful sunburn—it’s a vital tool in your long-term strategy to maintain healthy—and healthy-looking—skin.

Remember, UV rays can penetrate windows, affecting you indoors at work or while driving. It’s important to apply sunscreen even in these scenarios to ensure continuous protection. Other helpful tips include wearing wide-brimmed hats and protective clothing and seeking shade whenever possible, especially when the sun’s rays are strongest, usually between 10 a.m. and 2 p.m.

For more wellness updates, subscribe to The Healthy by Reader’s Digest newsletter and follow The Healthy on Facebook and Instagram. Keep reading:

• Here’s Exactly What to Look for in a Sunscreen
• 8 Ways Your Body Changes After Just One Sunburn
• 10 Sunscreen Myths You Believe That Make Dermatologists Cringe
• 11 Signs You Just Bought the Wrong Sunscreen