Yes, they do. Just like normal products they have their limitation. Usually, a single bottle lasts from 6-12 months. You should always see the label on the bottom to see its expiration date and use it based on that. However, if there is no label this means the purple shampoo won't expire. In that case, a good method to follow is to keep opened bottles for up to 18 months and intact bottles for up to 3 years. But always check the purple shampoo's condition. But it is best to be cautious of the purple shampoo's condition as expired purple shampoo may cause a harmful reaction, irritation, and unintended side effects.