What is the shelf life of my sunscreen?

Summer's here, and that means long days, plenty of sunshine and the opportunity to enjoy the great outdoors with your loved ones. As you prep for the many adventures ahead, sun protection should be at the top of your list of priorities. But before you reach for that dusty bottle of sunscreen you stored last fall, it may be wise to check the expiration date first!

Is last year's sunscreen still effective?

First and foremost, the best indicator of the current state of your old sunscreen is to look at the expiration date. According to the Skin Cancer Foundation, to test shelf life, manufacturers store a product at 40°C with 75 percent humidity; then at 40°C with 25 percent humidity; and then test it at 0, 1, 2 and 3 months.

Stability for three months in these laboratory conditions is comparable to three years in normal environments. In the vast majority of cases, you can reliably expect your sunscreen to last at least 3 years from the date you purchased it and the expiration date is a reliable indicator of its effectiveness.

In addition to the importance of the expiration date, you should also be mindful of the look and feel of the sunscreen to ensure that it hasn't broken down from one season to the next. The Mayo Clinic advises individuals and families to avoid previously-used sunscreens that may have obvious changes in color or consistency, as they may have lost their efficacy over time.

Where should I store my sunscreen?

At the end of each summer, most sunscreen is tucked away underneath the bathroom sink or stored in a closet, which may not be the best location for extending their shelf life. According to Drugs.com, sunscreen should be stored at room temperature, between 59 and 86 degrees Fahrenheit. Additionally, it should be kept in a dark space to prevent light from causing the ingredients to separate.

So, in most cases, the fluctuating temperature and humidity levels of bathrooms are not the ideal spots for storing sunscreen, so stick with the dark, room temperature closet, instead.