I had a very interesting question this morning, and I'd like to share it with you. I've changed it a bit to protect the privacy of the person who asked of course, but it lets me share some good information with you just the same. Thanks for asking such a good question J.
What are essential oils, and are they any different from any other oil? I've seen them in both plastic and glass containers, does that make a difference? I prefer plastic squeeze bottles for what I use. Do you have to store them in any special way?
My goodness you are asking a complicated question...I could write a book! Let's see if we can cover the basics...
All oils are chemically similar, and can come from plants or animals. Essential oils come from only plants, and are "single notes" ...the oil is from one plant only. "Essential oil blends" are a mixture of oils, usually with a particular effect in mind. Therapeutic "essential" oils are the ones that are prized for their fragrance, and their effects on mood and health that have been studied over the years. Other oils are less fragrant, and are not associated with mental or physical health effects...other than nutrition and cooking that is.
True essential oils are very strong, and need to be diluted. That is done by either just diffusing their scent into the air with a warmer or nebulizer, or putting them in "carrier oils" if they are for use in cosmetics or supporting physical health. Carrier oils can be healing in the effect they have on the skin, though. Some are better for dry skin, others for oily, some are good for all skin types...so the carrier is chosen for the purpose, and the type of skin . Some carriers have a fragrance of their own - sesame for example - which you can take into consideration in making a blend. Other carriers are by and large odorless.
Because they are totally natural with no preservatives, ALL oils need a little special care. Light, heat, and excess humidity can break down the oils and ruin their scent and effectiveness. It is important that they be kept in dark containers, in a dark, cool, dry place. Many cooking and carrier oils need to be refrigerated after opening so they don't go rancid. Some oils go rancid quickly, others are more stable and can last as much as a year if stored properly. When you are making a blend, adding a few drops of vitamin E (from a supplement capsule works) or jojoba oil to the carrier oil can extend freshness a bit.
Plastic containers are ok for end-product cosmetic uses like lotions and such...things you have made from essential oils and use in large enough quantities that they aren't sitting in the plastic container for very long...but never use plastic for storing the essential oils themselves or undiluted blends. Plastic is a petroleum product, and oil itself in a way. Over time, the oil and the plastic interact and you can damage the precious oil or leech chemicals from the plastic container into the oil. Dark brown or blue glass is always best if you can manage it. You can find them with the pump-type cap, which makes them almost as convenient as squeeze bottles. Glass containers for your home blends are available online and some health stores / organic grocers. If you are using an oil for a health goal or for fragrance, rather then just cosmetic / cleaning uses...then yes, avoid plastic.
I've never seen real, good quality oils packaged in plastic bottles anyway. Not everything called "aromatherapy" or "essential oils" in the market are actually that. It is very much "buyer beware". There are some cost effective, good quality suppliers online. I like www.aroma-pure.com, www.newdirectionsaromatics.com. In stores aura cacia and NOW are reliable brands. Aura Cacia is more for healing oils. NOW brand are very good oils, and even less expensive. I use those oils for cosmetic and household uses.
If you would like more information, I recommend "Aromatherapy Workbook" by Robert LeVebre, although there are many good books about aromatherapy on the market. I plan to ad mine to the lot within the next couple of years. Noelle Katai's TV show "Everybody Nose" is also informative and suggests some very nice blends.
I hope this helps, in a nutshell anyway. Feel free to send a follow up if you have questions about what we've covered here.
Good luck and enjoy using REAL good quality essential oils!