The official start of summer is tomorrow, but the sun has already made its presence well-known, persuading many of us to dig out the sunscreen.

A common behavior is to throw out the old and buy new every year, but a KARE 11 viewer wants us to VERIFY how long sunscreen is really good for?

Marian emailed us, saying "this morning I put sunblock on that I had purchased last year. Since I couldn't find any expiration date, I wondered if it is effective for more than one season?"

To answer Marian's question we turned to Dr. Jerry Brewer with the Mayo Clinic. He says sunscreens are designed to stay at their original strength for up to three years, but advises that they should be tossed if there are obvious changes in color or consistency.

Some sunscreens 'do' have an expiration date clearly printed on them, and Dr. Brewer says you should honor those dates. He suggests if the product you buy doesn't have one, write the day you bought it on the bottle, and throw it away after three years.

Keep in mind, if you use sunscreen often and apply it generously you won't have to worry about expiration dates.

Dr. Brewer says an average person needs about a 'shot glass' worth of sunscreen for every application, and that n average 4 ounce tube of sunscreen would fill that shot glass about 4 times.

That bottle empties quickly, especially if you're reapplying it every couple of hours.

So in conclusion... we have VERIFIED that in most cases sunscreen can last longer than one season, although it is important to check expiration dates.

SOURCE:

Dr. Jerry Brewer M.D., Mayo Clinic dermatologist