hunnymonster said:
Anything with a high moisture content (like creams, balms) might not be at it's best (dried out or separated slightly - probably nothing that a bloody good shake/stir wouldn't put right though) but it'll still be ok, so long as it's got sufficient anti-bacterial properties either naturally, or added.
In the food sense best before means exactly what you'd think... it's best to consume it before the date stated, but you won't die if you consume it a little bit after. Use by means that you really shouldn't use it after that date. Not sure if there such a distinction in cosmetics though?
Not really, but as you said, biodegradable thingies WITH water do go bad, and have expiry dates for a reason. The main problem here is fungal and bacterial growth. The more water, the higher the risk. ASB's have preservatives for a reason, but also have expiry dates for a reason.
The rule of thumb in home-made cosmetics is that anything with water in it (creams, milks) has a safe shelf life in the order of 6 months with adequate preservation, but days without.
Industrial stuff has (unopened) shelf lives that are much longer, since they can actually guarantee that production and bottling was done under sterile conditions, but will have a finite shelf life once opened.
Soaps have so little water that they can be stored almost indefinitely, even after opening (unless you keep your cake of shaving soap floating in a wet container -- any piece of soap will develop moulds under such conditions).
ASBs will go off eventually -- and the problem is that they may be truly off long before you actually see or smell the moulds (or bacteria), so you'd be well advised to take at least some notice of the expiry date.
Cream soaps are an odd product here -- they contain as much water as some cosmetic creams, but due to pH and nature of the major part of the solids (fatty acid salts) they will not readily succumb to microbial growth. But they will eventually...
Henk
