I’m constantly asked how long it takes for a sunscreen to expire. It is a very good question. No one wants to be out in the sun with an ineffective sunscreen.
My first response is fairly simple, your sunscreen should not last very long if you are using the appropriate amount of sunscreen and have incorporated it into your daily routine. Generally, you need about an ounce of sunscreen to cover the areas of the body that will be exposed to the sun. You’ll need more on days that you’ll be wearing less clothing, like going to the beach. Based on an ounce a day, you should run out of sunscreen before it expires.
Of course, this really doesn’t answer the question of how long a sunscreen lasts before it expires. Unless otherwise indicated by an expiration date, the FDA requires sunscreens to remain at their original strength for at least three years.
Sunscreens may have a shelf life of three years. However, sunscreens do become very unstable in high temperature. Ideally, you should store your sunscreen at a temperature of about 77º F. Therefore, storing your sunscreen in a hot car (which can reach temperatures of 120º or more) can cause your sunscreen to degrade and turn into a moisturizer with no sun protection.
I always recommend you throw your sunscreen in your cooler when you go to the beach. This will keep it from degrading and it will feel nice and cool when re-applying it to your skin. I also recommend that you replace your sunscreen yearly if you store it in your vehicle, boat, garage, golf bag, etc.