Many times we get calls from customers asking us if the oils are OK to store in colorless bottles because they are afraid that light will damage the oils.
Unfortunately many people have succumbed to the fear mongering and propaganda put forth by the makers of colored glass when it comes to storing essential oils. The amber glass makers will tell you that amber is best, the green glass makers will tell you that green is best, etc.
The truth is that most essential oils are photochemically inactive in the visible region and reactive in the ultra-violet (UV) region of the electromagnetic spectrum. Since UV light of high enough energy to cause photochemical reactions in most organic molecules is absorbed (not transmitted) by normal glass, regardless of color, it makes no difference if the oils are in brown, blue, green, purple or whatever color glass.
Of course there are a few exceptions, like with the chamazulene containing oils (blue chamomile, blue yarrow, blue tansy, etc.) that you would not want to store in colorless bottles for long periods under heavy lighting conditions. This is because chamazulene has strong absorption in the VISIBLE region of the spectrum (thus the intense dark blue color of these oils) and so it is the lower energy visible light and not just UV light that can significantly effect these oils.
But even so, thermal degradation and reaction with oxygen are the biggest enemies of these blue oils, which is why all of our chamazulene containing oils are refrigerated and stored under nitrogen, maintaining the nice dark blue color when you receive your shipment (many times you will find that other suppliers selling these oils will ship them after they have turned dark green due to oxidation from improper storage). I know many people will still believe they have to keep their oils in drab brown bottles, even after reading this, but I can tell you that based on the research I have done and my experience as a chemist, it makes no difference what color the bottle is for most the oils.
When I was doing my Ph.D. research at the University of Tennessee, part of my work involved doing organic photochemical reactions. To get these reactions to occur with UV light we could not even use normal clear glass containers because normal glass absorbed all the necessary UV light that would allow the reaction to occur. You can ask any photo-chemist and he or she will tell you that you have to use a special quartz reaction vessel to do these reactions because only quartz will give you the necessary transmission window to cause and photochemical change. But don’t take my word for it, do your own research. I can only give you the benefit of my experience and experiments as a Ph.D. chemist.
Sincerely,
Dr. Robert S. Pappas
