sunscreen, any more it is sweat-proof or waterproof. what do you recommend to your patients about reapplying? >> i think is ought to be reapplied, i'm not an expert on this, but just reading the data and so on, i would say every couple of hours. >> jamie: children more vulnerable? >> yes, they are and i would give to it them every hour but the main thing about these children is, keep them out of the sun for prolonged... don't let them sit in the sun prolonged periods of time. >> eric: especially the he wat the day, 10:00 to 2:00 or 11:00 to 12:00, and most sears times and the most sensible thing people can do, wear a hat or a cap. >> a hat with a brim. >> jamie: and you also recommend to sit in the sun or get a little bit of light or sunks maybe for 10 minutes a day, for the vitamin d, don't you. >> that's right, that is a very good point but that is not the same as sun bathing.