Neem oil is a natural product derived from the seeds and fruit of the evergreen neem tree. It is used in over a hundred pesticide products and has important applications in organic farming and medicines. It has been used as a pesticide for hundreds of years and is considered to be safe (1).
These days, neem oil is being touted as a natural alternative to synthetic preservatives.
Neem oil is a mixture of components and not a pure essential oil. Azadirachtin is the active component responsible for repelling and killing pests. The remaining components include fatty acids, essential oils, and other substances. Components of neem oil can also be found in other products such as toothpaste, cosmetics, soaps, pet shampoos, supplements, and medicine.
Most cosmetics include water as an ingredient (for emulsifying); therefore, preservatives are needed to prevent spoilage and the growth of bacteria.
If you have ever purchased an all-natural, preservative-free beauty product such as a face cream and discovered a “funky smell” before it was completely used up it means the product spoiled (i.e., contaminated by yeast, mold, bacteria or fungi). Unfortunately, these products produce natural sugars in a moist environment–the perfect breeding ground (complete with food source) for multiplying microbes. A product can look and smell just fine and still be contaminated. If the product is truly all-natural and preservative-free, it needs to be treated like food: made fresh in small batches and refrigerated (and remember, they will expire).
Products made with natural preservatives fair a bit better in terms of shelf life if used within 30 days after opening, but you might want to ask the question: how good are natural preservatives vs. synthetic preservatives at controlling and killing off any invaders to protect your product (and you)? Therefore, while there are effective, naturally derived preservatives, some can be weakened by exposure to air and water and thus cannot provide the same broad spectrum protection as synthetic preservatives.
Neem Oil as a Natural Preservative
When neem oil is used as a preservative, it functions as an antiseptic, anti-fungal, anti-bacterial, anti-viral, and anti-parasitic. Sounds pretty good, doesn’t it? And it’s used as a pesticide so it must be effective, right? (Although I doubt that argument would work in favor of synthetic preservatives!) Neem oil is effective at keeping oils from going rancid, but it doesn’t do as well protecting the product from bacteria and yeast because it is not a broad spectrum preservative. And it doesn’t seem to like water either. Bad news for technical managers and natural health promoters who want neem oil used as a preservative in water-containing cosmetics instead of the much more effective (and therefore safer) synthetic preservatives available for this purpose, such as Neolone 950. Strict regulations require such preservatives in order to kill all common pathogens. (See http://personalcaretruth.com/2010/06/why-cosmetics-need-preservatives/ for an excellent article on this matter.)
The half-life of neem oil in water is somewhere between one hour and four days. “Half-life” means that the concentration decreases by 50% in the measured time frame. If we take one day as the half-life for neem oil in water, with a reasonable average of the limits given, we would see the active concentration drop to 50% in one day, 25% in two days, 12.5% in three days, 6% in four days, 3% in five days and so on. By the time the product reaches the consumer from the day it is manufactured, the neem oil will have essentially completely disintegrated and be of no use as a preservative; therefore, a water-based product containing neem oil as the sole preservative is not protected from contamination (which poses a greater risk to your health than synthetic preservatives).
Consumers should be more aware of the occasional erroneous advice given by consumer protection groups, most notably Safe Cosmetics and the Environmental Working Group (and their skin deep database). We need to question these groups as critically as we question big industry in order to open up a dialogue. I am not sure why these groups get held up as the final authority. Is it because they validate our fears and suspicions of evil corporations? I don’t know, that’s just a guess. While their intentions may be sound, they often rely heavily on Material Safety Data Sheets (MSDSs)–which are usually available to the public–as one of their sources. MSDSs are useful, of course; however, people either forget or unaware that MSDSs provide safety procedures for workers in an industrial atmosphere to follow in the event of massive spills/exposures: these are “worst-case scenario” situations that never apply to the consumers of these products.
MSDSs are used to help set product stewardship and occupational safety and health guidelines for workers and emergency personnel who handle or work with the substance in large quantities. They are not intended for the consumer, but only for those in an occupational setting. It is important to remember when considering the safety issues of the products you are using that: “The dose makes the poison,” or, in this case, as preservative expert David Steinberg said, “Remember, Preservatives are Safer than Bacteria (TM).”
Back to neem oil. An organic chemist, like myself, would look at the chemical structure of azadirachtin, the active ingredient in neem oil, and know that it wouldn’t be stable in water, as we’ve previously discussed, but that it is easily fragmented by this reaction with water into smaller, useless pieces. Even though most of us aren’t organic chemists, this is easy enough to understand.
Neem oil is also hydrophobic, meaning that molecules are repelled from a mass of water. Therefore, in order to mix water and neem oil together (emulsify) for application purposes, certain surfactants must be added. And, sure enough, when you check the pesticide/farming literature, you find that the diluted product has to be used right away because of its limited shelf life. But not all products with neem oil have this disclaimer. It’s important to note that some neem oil containing products do remain “stable.” However, the product still loses its neem oil activity; it only continues to deliver pesticide activity by virtue of the other antimicrobials in the formula.
I don’t think anyone (cosmetic manufacturers, natural product suppliers, green retailers, etc.,) is trying to dupe the consumer. It’s more likely an issue of awareness (the lack thereof). Unfortunately, this kind of misinformation places the health of many customers at risk.