SPF testing is done on real people in a controlled laboratory setting. A small amount of sunscreen is applied to the skin and exposed to measured UV light so the lab can see how much protection it provides. To legally use SPF50, the test must follow strict rules including:
• at least 10 people
• the correct amount of sunscreen applied
• a calibrated UV source
• checking the skin the next day for redness
• strict analysis to calculate the final SPF number
This is the method recognised in Australia and internationally.