How to Use Up Those Old and Aging Essential Oils
Within this article, all volatile oils including essential oils, absolutes and CO2s are collectively referred to as "essential oils."
Over time, essential oils can oxidize and gradually lose their therapeutic value. The aroma of essential oils also can change over time.
If an oil smells really weak or dramatically different after a period of time, it's best to dispose of it and not try to find a suitable use for it.
Essential oils that have aged and no longer possess the fresh, full aroma that it used to have are no longer considered therapeutic. Avoid using such oils in any aromatherapy products or application that will come into direct contact with your skin. Old oils should also be avoided in room sprays and diffusion applications where people and pets can directly inhale the volatile components of the oil.
Not all essential oils age poorly. Patchouli and sandalwood are two examples of oils that can mature beautifully with age, however their therapeutic benefits can also change. See the Essential Oil Shelf Life article for guidelines on the life span of essential oils.
If you can tell that an aging essential oil smells weak but still aromatically pleasant, there are a few ways that you can still get some value out of that aging oil:
Add 1-2 drops of your aging essential oil to a stale/smelly drain to help disinfect and eliminate the odor. Do not pour more than 1-2 drops down your drain as essential oils can harm water supplies and it's possible that essential oils may harm certain types of pipes or fittings. See the Essential Oil Disposal article for more information.
Trash Receptacle Freshener
Sprinkle 1-2 drops of essential oil onto your trash to help eliminate odors and detract insects and rodents. Peppermint is especially helpful in detracting rodents.
Aging essential oils can be used in place of your newer essential oils within your household cleaning formulations, blends and recipes. Remember, however, that oils that have oxidized can be harsher and pose more risk of skin sensitization, so greater care to protect your skin during use would be prudent.
Vacuum Bag Freshener
Depending on your vacuum model, add a drop or two to your vacuum bag.
Insect and Rodent Repellent
Citronella, Lavender and a number of other essential oils can help deter insects. Peppermint is amongst those that can help deter rodents. Remember that essential oils can harm fabrics, furniture and floor coverings, so care must be taken in your choice of implementation.