Eli5: How come hand sanitizer has an expiration date? What exactly happens once it goes past it?

Question

Eli5: How come hand sanitizer has an expiration date? What exactly happens once it goes past it?

In: Chemistry

Answer 1

The sanitizer and the bottles are not completely chemically stable. There are some chemical reactions happening athough they are slow. This means that the chemicals change over time. For example the plastic bottles may slowly dissolve into the liquid. The chemicals in the liquid itself might react to each other turning into other chemicals. A big problem can be that the alcohol reacts with oxygen or other oxidizers and turns into vinigar. The chemicals might also be emultifications which will slowly seperate over time so you get different layers with different chemicals. A handfull of gel will do nothing if the alcohol have seperated into a seperate layer.