Do essential oils have an expiration date?

Do essential oil Have an Expiration Date?

Q: Do essential oils have an expiration date? The sales assistant at the counter said that essential oils get better with age. Is that true?

A: Everything in nature ages, so everything has an expiration date, just in varying lengths. Strictly speaking, the antioxidant and preservative properties of essential oils are sufficient to provide antibacterial and anti-aging benefits to organisms. This is because plants undergo a continuous process of evolution, gradually transforming from their original terpenes, phenols, alcohols, and esters. Therefore, any essential oil has the potential to improve with age! However, once opened, it continuously transforms and loses certain substances during contact with air (this is not the same as food spoiling upon expiration), hence the concept of an expiration date.

Fruits have the shortest growth period, resulting in the most unstable molecules that are easily transformed, thus having the shortest shelf life after opening.
Flowering periods are typically short, resulting in less stable molecules;
Herbaceous essential oils are next, but still relatively fragile;
Woody essential oils are the most stable because the growth process from tree to harvest for essential oil extraction is already highly mature, leading to the most complex and stable molecules, and thus the highest phytoncides content. Among woody essential oils, resins are the most stable, often described as improving with age, such as sandalwood, frankincense, myrrh, and benzoin.

Pure single essential oils are easier to preserve, followed by pure blends. Blended essential oils, whether floral or herbaceous, have a shorter shelf life. Some commercially available blends, which already contain a carrier oil (for direct skin application), have the shortest shelf life after opening due to the volatile nature of plant oils.