What is sunblock?
Sunscreen and sunblock are two forms of defense against the sun's rays which may cause damage to the skin or cause skin cancer if you have too much exposure. Sunscreen uses chemicals as a defense to prevent the skin from absorbing UV rays. Sunblock, however, is a physical defense for the skin, sitting atop the skin, working as a barrier to prevent the skin from absorbing UV rays. Sunscreen rubs in and becomes invisible, sunblock is opaque and can be seen on the skin once applied.
Does sunblock expire?
Sunblock and sunscreens are required by the FDA to keep to their original strength for three years. Some sunblock will include an expiration date on the package, indicating when it will no longer be at full-strength. If you purchase a sunblock without the date, it's recommended you use it within three years of purchase.
How long does sunblock last?
Sunscreen usually lasts for up to two hours after application, both on sunny and cloudy days. Most sunblock and sunscreen packaging will indicate if the time of effectiveness is longer or shorter than this.
Can you tan with sunblock?
Sunscreen and sunblock will likely preventing your skin from tanning to some degree. You may still get a slight tan, though no amount of deliberate tanning is considered safe or healthy.