It is sometimes convenient to categorize packages by layer or function: primary, secondary, etc. 1  Primary packaging is the material that first envelops the product and holds it. This usually is the smallest unit of distribution or use and is the package which is in direct contact with the contents.
Sunscreen does not stop working the day after the expiration date. Sunscreen is usually effective for at least three years, which is usually longer than the expiration date marked. What to Look for When You have Allergies or Sensitive Skin. Skin allergies can be a common problem. For individuals with sensitive skin, try physical sunscreens. Physical sunscreen protects your skin by deflecting or blocking the sun's rays, while chemical sunscreens absorb the sun's rays.
I'm not sure how long sunscreen is supposed to stay good, but when I was a kid we had a bottle that lasted us a few years, not sure whether it had an expiration date. I'm pretty sure it still did the job after those few years though. I'd say that sunscreen likely stays good for *at least* 1 full year.