Putting on an old sunscreen may cause more harm than good. If you’re using expired sunscreen, the sun may be damaging your skin more than you realize. It’s important to use sun protection products that are fresh and effective.
There are two forms of sunscreen: physical blockers and chemical blockers. Physical blockers, such as zinc and titanium, reflect light away from the skin. Chemical blockers, such as avobenzone, actually absorb the light and prevent it from reaching the skin.
Some sunscreens -- particularly chemical blockers -- have an expiration date because the ingredients degrade over time. Once the expiration date has passed, it is best to discard the product since it may not perform as it should. If the sunscreen does not have an expiration date, make sure to note the date you bought it and get rid of it after three years.
If you don’t know when a product was purchased and there’s no expiration date, then use common sense: If the product is clumpy or has a foul smell, throw it away. When it comes to sunscreens, err on the safe side to avoid a false sense of protection and imminent sunburn.
