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When Good Oils Go Bad: What Makes an Oil Smell Rancid?

Posted by Sharon Gnatt Epel on

Has this ever happened to you? You go to your favorite natural food store to pick up a few items, find yourself in the cosmetics aisle and notice an appealing display stacked with colorfully labeled bottles of natural perfumes, lotions and exotic oils. You open a tester, close your eyes, take a deep sniff, and recoil in horror! OMG! How can anyone use this natural stuff, you think to yourself. It smells absolutely awful!

Unfortunately, this is the introduction most of us have had to the world of essential oils and natural perfumes. Natural food stores are notorious for not checking the tester displays to make sure that the contents are still fresh and viable. Some stores deflect the responsibility entirely and expect the product manufacturer to send reps to check this for them, but most small organic companies do not have enough time or adequate local representation to do this. The majority of store managers don’t even check for product expiration dates, leaving the consumer to figure it out on their own.

So, what is rancidity and how do you know when an oil-based product has gone bad?

Rancidity occurs when oils oxidize (are exposed to air). On the simplest level, this is a factor of how many times a bottle has been opened and closed. Most oils smell and taste best when they are fresh. If you think of the just-made-after-harvest period as the beginning of the freshness timeline, the amount of time that it takes for an oil to go rancid depends upon many factors, including exposure to air and light, the temperature at which the oil has been stored, and the amount of natural antioxidants it contained in the first place. Therefore, it is extremely important to start out with a high-quality oil. Americans have become so accustomed to some degree of rancidity that they often cannot identify it until it hits the opposite extreme-end of the freshness spectrum and smells musty and weird.

All oils eventually go bad. This is why it is foolish to hoard an oil-based product, and why La Ishá’s skin care comes in convenient 3-month sizes, even though our average shelf-life is 8 to 10 months. If you have been “savoring” a precious bottle of Breast SOS and still have it one year later, you have not been using it as designed, nor taking advantage of its many benefits.

What about the “Best by” dates that are stamped on so many products? Unfortunately, they don’t tell you when the contents were harvested and milled, which is the most reliable indicator of freshness since it tells you when the oil was made. 

So aside from having a nasty smell, what is so terrible about using a rancid oil? Rancid oils (especially in the foods we eat) can develop toxic compounds that are linked to cancer, advanced aging, neurological disorders and heart disease. If you are someone who buys huge sizes of olive oil at your local Costco or Sam’s Club and doesn’t use them up quickly, you might want to rethink your purchasing habits. Unless you own a restaurant, most people cannot finish these enormous sizes before they go rancid.

This extends to beauty products as well. Mainstream cosmetics manufacturers generally infuse their formulas with synthetic preservatives to give it a very long, stable shelf-life, but some of these chemicals have been linked to breast cancer, deformities in newborns, neurological disorders and a wide array of health-risks. On the other hand, if you opt for “preservative-free” skincare, you should know that anything that contains water opens the door to bacterial, mold and microbial contamination. What’s an educated consumer to do?

  1. Not all preservatives are bad. Natural skin care lines that boast they are 100% preservative-free are downright dangerous. Any products that contain water and do not use some kind of a preservative system are very risky. Look for an oil-based product line that contains a natural preservative system, and includes some form of natural, non-GMO vitamin E (tocopherol) and/or rosemary oil. These ingredients can help increase shelf-life and delay rancidity.
  2. Skin care preparations that contain base carrier oils including grape seed, almond, and borage have the shortest life span, along with citrus oils. Extra care should be taken to store them away from sources of heat and light. Refrigeration can also help. FYI, essential oils do not turn rancid like vegetable oils: they simply degrade and diminish in efficacy over time. Coconut oil, fractionated coconut oil and jojoba oil (which is actually a natural liquid wax) will stay viable for many years.
  3. Make sure that the beauty products you purchase are manufactured by companies that have integrity and believe in full ingredient disclosure. That’s the best way to avoid inferior quality components, toxic reactions and costly mistakes.
  4. Ask if the company that manufacturers your favorite products follows FDA guidelines for GMP (Good Manufacturing Practices). This will help ensure that they subscribe to high quality standards.


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