We all have 'em -- old bottles and tubes of old shampoo tucked away in drawers and cabinets in the bathroom. But are they safe to use?
If the product is opened, it should be used within 18 months. If unopened it should be OK to use by three years. If you can't remember when you opened the product, give it a good sniff. If it smells off, throw it out. Or if the product doesn't lather, it's not going to get your hair clean, so best to toss it.
If you use an expired product, your hair will probably end up being dull and greasy at best. At worst, it could be infected with bacteria and will give you a rash.(Real Simple)