So you stroll into the drug store to snap up a bottle of sunscreen and find yourself facing a wall of products plastered with jargon about SPF, UVB, UVA and ingredients that look like entries in a Bulgarian dictionary. And every summer there seems to be news about how much protection they really give you and whether all those chemicals are really safe.

How do you make sense of it all? Here's what you need to know:

• Form. Sunscreens don't just come in lotions anymore. You also have your choice of gels, ointments, creams, wax sticks, sprays and moist towelettes. People prone to acne may benefit from a gel or water-based formula. For those with sensitive skin, creams are usually less irritating than gels or lotions. Creams are also a good choice for people with dry skin. People with certain allergic reactions may benefit from a physical sunscreen that contains zinc oxide or titanium dioxide.
  
  
• Rays. Two types of invisible solar radiation reach your skin: ultraviolet A (UVA) and ultraviolet B (UVB). Both can cause sunburn and skin cancer, especially UVB. Experts recommend a product that blocks both rays. The U.S. Food and Drug Administration hasn't yet approved a rating system for UVA protection, but the products that block most UVB also generally block some UVA.
  
  
• Strength. This is rated in sun protection factor (SPF), which indicates how long you can be in the sun before getting burned. It's calculated by comparing the times for UVB to burn unprotected and protected skin. For example, if an unprotected light-skinned person begins burning in 10 minutes, a 15-SPF sunscreen would shield that individual's skin for 150 minutes.
  
  An SPF of 2 blocks 50 percent of UVB rays, and an SPF of 15 blocks 93 percent. Be aware, though, there are diminishing returns the higher you go. An SPF of 30 blocks 97 percent of UVB, but SPFs of 50 or 60, which some products boast, don't provide much more protection. The American Academy of Dermatology (AAD) recommends that you should use at least SPF 15, preferably in a waterproof or water-resistant product.
  
  
• Ingredients. The two main types of sunscreens are chemical and physical agents. Chemical sunscreens absorb UV rays, whereas physical sunscreens absorb, block, reflect or scatter UV rays away from the skin. Ingredients that extend coverage beyond the UVB range and into the UVA range include the chemicals benzophenones (oxybenzone), cinnamates (octylmethyl cinnamate and cinoxate), sulisobenzone, salicylates -- and the physical agents titanium dioxide, zinc oxide, helioplex, mexoryl and avobenzone (Parsol 1789). Dermatologists recommend products that include a physical blocking agent for the best protection against UVA and UVB rays.
  
  Some environmental groups have raised health concerns about chemical sunscreens, particularly oxybenzone, which is absorbed in the skin. Many doctors find the evidence for harm scientifically weak. But if you are concerned, you can make sure you stay protected from ultraviolet light by applying a physical agent sunscreen instead, or simply wear protective clothing.
  
  
• Application. A few minutes in the sun provides vitamin D, but use sunscreen whenever you're going to be outside for 10 minutes or more, even on overcast days. Apply generously to dry skin about 20 to 30 minutes before going outside, including your eyelids, nose, ears, neck, hands and feet. Reapply every two hours and after sweating and swimming, even if the product is marked as waterproof. A wide-brimmed hat and tightly woven, loose-fitting clothes also help.
  
  
• Kid stuff. Because the safety of sunscreen use on infants younger than 6 months has not been established, discuss sunscreen with your baby's pediatrician before using the product. For kids older than 6 months, use sunscreen that is especially made for children.
  
  
• Those lips, those eyes. Don't forget your kisser. Use lip balm that contains sunscreen, and reapply it every hour. And protect those peepers -- wear sunglasses, and when exercising wear a headband to keep sunscreen from stinging your baby blues.