Sunscreen Checker

Sunscreen Science, Answered

The questions people actually ask about sunscreen — answered clearly, with references, by Dr. Erah Anwar, PhD.

Sunscreen Basics

  • Chemical vs Mineral Sunscreen: What's the Difference?

    The real difference between chemical and mineral sunscreen — how each protects your skin, how to tell which you have from the ingredient list, and why the naming is misleading.

  • Sunscreen vs Sunblock: Is There a Difference?

    “Sunscreen” and “sunblock” describe the same kind of product — and US regulators no longer allow the word “sunblock.” What actually matters on the label instead.

  • How Does Sunscreen Work?

    Sunscreen works by absorbing UV radiation before it damages your skin. How UV filters actually work — and why the “mineral reflects, chemical absorbs” idea is mostly a myth.

Using Sunscreen

  • Does Sunscreen Expire?

    Yes — sunscreen expires, and using it past its date can leave you underprotected. How to read the date, what changes, and how to store it so it lasts.

  • Can You Still Tan With Sunscreen?

    Yes, you can still tan with sunscreen — no product blocks all UV and most people underapply. But a tan is a sign of DNA damage, not health. What that really means.

  • How Much Sunscreen Do You Need, and How Often?

    About a shot-glass for the body and two fingers' worth for the face, reapplied every two hours. Most people use far too little — here's how to get the SPF you paid for.

  • Sunscreen or Moisturizer First?

    Moisturizer first, sunscreen last. Sunscreen should be the final skincare step before makeup — here's why, and how long to wait between layers.

Skin Types & Conditions