Depending on the oil there are some ways to tell if it has expired. For example, citrus oils like lemon and orange can start to emit a distinctive scent, although this may not be as noticeable in other types of oils. If you think that your essential oil does have a different scent, then do not apply it to your skin as it could cause an allergic reaction. Colour changes can also occur, as is the case with peppermint and chamomile, while other oils may display a slight shift away from their original colour. Another thing to look out for is that the consistency of the oil may have changed. If it is thicker or thinner than usual this will usually mean that its composition has altered, and you may need to buy a replacement. Before you buy an essential oil, you should check that it comes with an expiry date. At Nikura, all our essential oils come with an expiry date so you know that it will last for a certain amount of time if the storage instructions are closely followed.