Nicole writes: "I sunburn quite easily and have been very diligent in applying sunscreen when out in the sun. It seems as long as I leave the sunscreen on, I don't burn. But as soon as I shower and sit in my house, the rest of the night a burn develops - sometimes a significant one. Can the ultraviolet rays be stored in your skin somehow to later burn?"
Although ultraviolet rays are not stored in the skin, the skin's reaction to them does that some time to develop. Most sunburns reach their maximum intensity between 12 and 24 hours after exposure. That means you need to keep the skin protected on subsequent days since it could still be reacting to a prior skin exposure. One thing we are finding out is that some of the lower SPF sunscreens that dermatologists recommend for sea level exposure, SPF 15, might not cut it here at a higher altitude. Small studies have shown much better protection with higher SPF lotions. The other key is to make sure you reapply every 2 hours while out in the sun.
Larry writes: "Does sunscreen have a shelf life? I've heard 2 years and even up to 3 years."
Sunscreens can lose their ability to protect your skin over time. Some bottles come with an expiration date. They should be thrown out after that date. If they don't have a date, your best bet is to get rid of them after three years.
Sherri writes: "I had an eye doctor tell me not to use self tanning lotions because of cancer risks from the chemicals. What about spray tans?"
Spray on tans contain a chemical known as DHA, or dihydroxyacetone. This chemical, and the spray tans that use it, is generally considered safe if used according to the directions. The FDA has put out a warning about this chemical. The FDA says:
"Consequently, FDA advises asking the following questions when considering commercial facilities where DHA is applied by spraying or misting:
- Are consumers protected from exposure in the entire area of the eyes, in addition to the eyes themselves?
- Are consumers protected from exposure on the lips and all parts of the body covered by mucous membrane?
- Are consumers protected from internal exposure cased by inhaling or ingesting the product? If the answer to any of these questions is 'no,' the consumer is not protected from the unapproved use of this color additive. Consumers should request measures to protect their eyes and mucous membranes and prevent inhalation."
In other words, if you can cover your mouth, nose and eyes during the spray tanning process, then you'll be less likely to ingest the chemical. Otherwise, these types of indoor spray tans are typically considered safe.