Sunscreens come in the form of ointments, lotions, gels, sprays and even in waxy sticks. All carry the initials SPF, or sunburn protection factor, followed by a number. The higher the number, the stronger the protection against the sun. Dermatologists recommend that you wear sunscreen with an SPF of at least 30, even on cloudy days. A high SPF does not mean you can safely stay in the sun longer. Rather, it allows you enhanced protection as long as you do not stay in the sun too long.
A sunscreen with an SPF rating only protects against UVB rays. These are the weaker tanning rays that can penetrate only the first skin layer. They can tan and even burn the skin, but do not penetrate as deeply as UVA rays do.
Broad-spectrum sunscreens that protect against both UVB and UVA rays have become more widely available since the summer of 2009. Look for the words, oxybenzone, avobenzone (Parsol 1789), or Mexoryl on the list of ingredients. If they are there, the product blocks UVA rays.
People prone to skin allergies prefer sunscreens that contain titanium dioxide and/or zinc oxide. These physically reflect UVA rays instead of blocking them.