I thought I knew the answer to this one, but went to the FDA website to check it out first. The site is really helpful- you just have to keep searching, because there is SO MUCH information, and some of it is really buried!!
One of the best resources they have, is a collection of warning letters that have been sent to other soap and cosmetic makers. In them, the violations are listed... and interestingly, not one of them that I read took issue with manufacturers putting "saponified blend of" or "saponified (insert kind) oil." I thought for sure they would not agree with that labeling. I only put the oils I use. I don't list sodium hydroxide, because according to the FDA, you are only required to state the ingredients in your finished product... not all the steps used to get there. And, hopefully- there is no lye in my finished soap!!!
I didn't see any specific mention of listing individual essential oils, either However, the FDA guidelines clearly require "each ingredient" to be listed, in the order of their amount, so that consumers know what they are purchasing. The intent of the labeling guidelines is to allow consumers to make good decisions about what they're purchasing. So, if someone is allergic to cinnamon oil, and they don't see that on the label, they can purchase it, knowing it is not in there. If you simply state "a blend of essential oils" this does not give consumers the information they need to make informed decisions. I think this sets you up for liability issues, as well as letters from the FDA about misleading the public.
Another important issue with FDA and soap, is whether your product is a soap, or a cosmetic. They are very clear here, that if, in any way, you claim, or imply that your product will treat or help ANY sort of skin condition, including something as simple as your soap will "moisturize dry skin," this makes it a cosmetic in the eyes of the FDA. I don't mess around with this. ALL of my soaps are labeled as if they are cosmetics- just in case. Even saying "Lavender has been known throughout the centuries to induce relaxation" on your website, implies to the FDA that you are adding lavender to your soap to induce relaxation. They state that what is important here, is what the CONSUMER believes your product will do for them, even if you don't state it directly. One step of their investigative procedure, involves asking your customers what they believed your product was capable of. So, be very careful with your statements. And, carry liability insurance. I don't want to lose my home or lifestyle, because of someone like the ones who sued McDonald's over hot coffee.
For an example FDA warning letter, check out:
http://www.fda.gov/ICECI/EnforcementAct ... 076551.htm
This company manufactures all sorts of things, including soap, and it is definitely worth a look.