Imagine this. You get your peppermint essential oil bottle and use it with no issues. The following day the weather is super cold and you tip the bottle up to get a couple of drops in to your aroma diffuser and nothing comes out. You know that the bottle is still 3/4 fill. What's happening?
Your peppermint essential oil has crystalized and now it's solid. Has it gone off? Should I throw it away? Absolutely not. This is perfectly normal for peppermint. It also happens to pure rose essential oil at a much higher temperature. There are not many essential oils that this happens with, but these are the main two.
Peppermint essential oil is high in menthol. In cold temperatures, it will crystalize naturally, in the same way that coconut oil is usually solid in the jar, but once it hits around 25°C it starts turning to liquid. Don't remove the orifice reducer and take a look inside. All you need to do is warm it back up again. Eco Modern Essentials have a note in their FAQ about it. Many other brands have information on it.
How to warm up your peppermint essential oil
Depending on how cold and solid the oil is, there are a couple of ways to do this.
The most gentle way to warm up your peppermint essential oil is to warm the bottle in your hands. You can even tuck it down your bra or somewhere that it will be against your skin. Let our bodies natural warmth heat it up. Please ensure the lid is on securely and there are no spillages on the outside of the bottle as essential oils should not be put on the skin neat (undiluted). If you do happen to accidentally spill it on your skin neat, do not wash it off with water. The first thing you need to do is to dilute it with a carrier oil. You can use fractionated coconut oil or jojoba oil if you have it handy. If you don't, walk to the pantry and grab a bottle of olive oil or anything you have on hand.
The quicker way to warm up your peppermint essential oil is to run the bottle under warm water. Again, ensure the lid is on tight as you don't want to dilute your essential oil with tap water. If you don't like this being wasteful, get a glass and put warm water in the glass and let the bottle float in it.
Regardless of which method you choose, let the bottle get warm and swirl it until you get the desired effect - ie: a liquid state again.
It doesn't matter if it's a cheap brand or an expensive one, all peppermint essential oil has the capacity to do this.