1) Putting on the sunscreen just before going into the sun
Chemical barrier sunscreen works by changing UV rays into heat, then releasing that heat from the skin. In order for this to be effective, you need to apply it 20 -30 minutes before heading out into the sun. Slapping that oxybenzone/ octinoxate / octisalate /avobenzone suncreen on seconds before heading into the sun isn’t going to protect you right away.
If you are a “last minute sunscreen” person, consider using mineral sunscreen. It is a physical barrier, no chemical reaction required- the zinc and titanium oxides reflect the sun rays off your skin. Bonus, mineral sunscreen won’t kill the coral and fish you love so much on your vacations!
2) Not reapplying often enough
Time flies when you’re having fun. But, you sunscreen doesn’t work forever. Read the instructions on your sunscreen and reapply as directed. Sometimes it’s every 2 hours. It’s less if you are swimming or sweating a lot. Consider setting an alarm on your phone to make sure you reapply.
3) Reapplying on wet skin
It never occurred to me that this was a problem until I was sitting on a beach and saw a parent apply sunscreen to their dripping wet child. I saw how the sunscreen didn’t really even stick to the kid, didn’t go on evenly and probably washed off as soon as the child went back into the water. Dry the skin first then reapply the sunscreen.
Don’t forget, even on cloudy days, the sun’s UV rays make their way through and you can get a sunburn.
In addition to proper sunscreen use, for the best sun safety, try to avoid being in the sun for extended periods of time between 10am and 2pm; wear hats, sunglasses and long, light clothing, if possible.