Trying to explain how much SPF you need to put on is difficult enough but when it is my 13 year old son! I found this article by healthyhub which has really helped, he can now visualise the amount needed for each area and it is easy to get the coins out to check the correct amounts used. Always use a SPF 30 or above and remember to reapply it every 2 hours. Today we will be using Vitage spf 30 & Medik8 both are very good.