How do I know if sunscreen is working?

You cannot feel sunscreen working, which is part of why consistent use matters. Indicators that your sunscreen is doing its job include not tanning or burning during typical daily outdoor activity, and noticing that your skin tone stays more even over time. SPF does not create a sensory experience you can feel.

The effects of sunscreen are most visible in the long term. People who use sunscreen consistently for years typically see slower progression of sun spots, more even skin tone, and fewer visible signs of UV-induced ageing compared to those who skip it. Short-term, if you are spending time in strong sun and not burning, your sunscreen is effective. If you tan significantly or burn despite regular application, you may be applying too little, missing areas, or not reapplying. Using the correct amount (3-finger rule for the face) and reapplying every two hours when outdoors are the most important practical steps.