One of the effects of sunburn is a drying of the skin. Ultraviolet radiation depletes the skin of antioxidants, which allows for peroxidation -- a deterioration of lipids in the skin. Lipids are fatty acids that serve as the binding between the dead skin cells that form the outermost layer of the skin, or the horny layer. Together, the lipids and dead skin cells produce a waterproof barrier that maintains moisture in the skin.
When lipids are destroyed as the result of overexposure to the sun and cause sunburn, skin experiences a pronounced loss of moisture. In other words, it's more important than ever to moisturize skin when you have sunburn. Keep your skin as moisturized as possible to aid in its recovery; apply moisturizer as often as possible. Be sure you have the proper moisturizer, however. There are some types of moisturizing agents that can help restore skin to its natural state more quickly that you might want to look for.
Chief among these are humectants. A humectant is any kind of hygroscopic substance -- one that not only maintains moisture, it strips it from the surrounding air. Aloe vera is a naturally occurring humectant that has the added bonus of soothing warm, sunburned skin. Other examples of natural humectants include alpha hydroxides like lactic acid, oils derived from plants and animals and even honey. Alpha hydroxy acids (AHA) hasten the process by which skin cells are sloughed off and replaced, which can speed up the healing process for sunburns. Be careful not to use too potent an AHA, however, as it could exfoliate skin too harshly.
Most moisturizers contain humectants and many also contain emollients. You may want to avoid moisturizers that contain emollients when you have a sunburn, as one of the common reactions to emollients is a mild skin irritation, which isn't something you want on top of a sunburn [source: DermNet NZ].
Because of the possibility of an adverse reaction, periods when you have sunburn aren't good times to be adventurous in testing out new moisturizers. If you already have a tried and true moisturizer you swear by, stick to that; it should do the trick. Going for a moisturizer that has as few ingredients as possible is also a good idea.
Vitamin A and E oils make excellent moisturizers, since they're packed with nutrients skin needs to function in a healthy manner. Be careful what vehicles these A and E moisturizers use to deliver the nutrients, however. Look for plant derived oils, like coconut, avocado or almond oil. Avoid mineral oils bases, as the petroleum can actually prevent absorption of the vitamins.
There's also an often overlooked product you can find anywhere that can help moisturize sunburns: Noxzema. The cold cream and makeup remover was originally developed as a sunburn remedy and still works well as a moisturizer and cooling agent for bad burns.
Treat your skin with extra attention and moisture, and you'll find your sunburn leaves much less of a mark and will heal much more quickly.