We all know that sunscreen is your best defense against the sun’s harmful rays, which can cause sunburn, premature aging, and increase your risk of skin cancer. What’s less clear is how to select the right product, how much to use, and how to apply it effectively.
Here we break down the basics of sunscreen so you can confidently choose and use the product that suits you best.
How to Pick the Right Sunscreen
With over 2,200 options sunscreen options on shelves, it’s easy to get overwhelmed when deciding which to buy. While their forms may vary from sprays, lotions, and sticks, one thing all sunscreens have in common is SPF.
SPF stands for Sun Protection Factor. It's a measure of how well a sunscreen protects your skin from UVB rays, which are responsible for producing sunburn and play a major role in skin cancer. However, SPF does not reflect how well a product protects against UVA rays, which penetrate the skin more deeply than UVB rays, and are associated with skin aging and cancer, such as melanoma.
Most dermatologists recommend using products that offer SPF protection of at least 30, AND “broad-spectrum protection” against UVA rays.
If your plans involve water activities, look for a water-resistant product. NOTE: While these products stay on the skin longer than other sunscreen products when swimming, they still need to be reapplied.
How Much Sunscreen Should You Use?
Most people don’t use enough sunscreen, which means they aren’t getting the protection promised on the label. Here’s a simple way to remember how much you need:
- For your whole body: Use about 1 ounce (think a shot glass or golf ball size) to cover all exposed skin.
- For your face and neck: Use about 1/4 to 1/2 teaspoon, or a dollop the size of a nickel. Some experts also recommend the “two-finger rule”—a line of sunscreen along the length of two fingers for your face and neck.
- Don’t forget tricky spots: Ears, the tops of feet, behind the neck, and even your lips (use an SPF lip balm).
When and How to Apply
Sunscreen can be applied before or after moisturizer, depending on your preference. The key is to use it consistently and to use enough and cover all exposed skin.
- Apply early: Apply sunscreen 15–30 minutes before heading outside so your skin has time to absorb it.
- Reapply often: Every two hours, or immediately after swimming, sweating, or towel-drying—even if your sunscreen is labeled water-resistant.
- Be generous: It’s better to use too much than too little, as using too little reduces protection and increases your risk of burning and sun damage.
- Use every day: UV rays penetrate clouds and glass, so daily use is important—even when it’s overcast or you’re indoors near windows.
Bear in mind that even the most carefully selected sunscreen loses effectiveness over time. Replace any product that is past its expiration date or has changed in color or consistency
Finally, sunscreen is just one means of protecting yourself from damaging rays. Whenever you reach for the sunscreen, you may also want to grab a wide-brimmed hat, sunglasses, and sun-resistant clothing for increased protection.
Lixia Ellis, MD, PhD is a board-certified dermatologist at SVMC Dermatology.