Fun in the Sun:

Sunscreen Tips and Links

Before going out to have fun in the sun, you should apply sunscreen to yourself and your child. Reapply sunscreen every 2 hours, and after every time you get wet or sandy (rubbing the sunscreen off). Harmful UV rays come through clouds, so a cloudy day is no excuse to skip the screen.

SPF 30-50 are best. SPFs that are higher than that do not add significantly more protection.

The safest sunscreens are barrier sunscreens. These are sunscreens that use zinc oxide or titanium dioxide as the active ingredient, which sit on the skin to provide a shield from the sun. Since they are not absorbed systemically, I recommend using only these types of sunscreens* on infants (in addition to shielding clothing and hats).

Chemical sunscreens are those that contain chemicals which are absorbed into the skin to provide protection. These are newer, but still safe when used correctly. Some of the active ingredients in chemical sunscreens include, but are not limited to, octinoxate, octocryleme, oxybenzone. Most sunscreens on the market today use these, and there are many more options that kids like with these formulations, such as sprays, colors, and different textures. The best sunscreen is the one you can actually get on your child everyday. The aerosol spray sunscreen versions should only be used outside, in well ventilated areas, and below the neck, because they are meant to be sprayed evenly on the skin (you should see a layer of sunscreen forming), and not breathed in. They are a quick way to reapply sunscreen on kids at the beach or park, but can be avoided at home.

A lot of people are wondering about vitamin D. Although our skin can make vitamin D by being exposed to UVB light from the sun, the amount of sun it takes is variable by region and skin type, and enough sun to make enough vitamin D will also increase skin aging/wrinkles and cancer risks, so I still recommend using sunscreen, then getting vitamin D in your diet. For more information, see
http://www.vitamindcouncil.org/about-vitamin-d/how-do-i-get-the-vitamin-d-my-body-needs/

Do not use combination insect-repellent and sunscreen mixes. Insect repellents should not be applied more than once per day, and should not be applied to babies. For more information on insect repellents see here and here.

I used to link to the Environmental Working Group's sunscreen ratings, but their methodology has been ignoring science, and based on fear-mongering lately, so I stopped. For more information on that, see here and here.
EWG also warned against "nano particles" with no scientific basis. For information on them see this article from cancer.org.

*Here are some examples of sunscreens that use barrier (mineral) ingredients, in alphabetical order:
Aveeno Mineral Block
BabyGanics Cover-Up Baby Pure Mineral Sunscreen Stick
Banana Boat Natural Reflect Sunscreen
Burt's Bees Baby Bee Sunscreen
California Baby Sunscreen
Mustela Sun Cream and Sun Lotion
Neutrogena Baby Pure and Free

Here my son demonstrates proper beach attire with sunscreen (c) 2011