Thats definitely not something I would want. I was hoping that a small amount would only color the soap. Maybe I'll test out a little next time I soap, I can save out enough for a bar or two and just put in a big pinch.
Wonder if it would be better to use dry henna or some that has been prepared and has full dye release?
I understand a bit about henna from my hairdressing days. It's not something I would want to use in soap at all. It can color many things, including you and your hair. No idea what would happen in soap, but it's an odd colorant to be sure.
Known fact, hair colored with certain types of henna reacts oddly to other chemical processes. If you ever use it, be sure how it will react before doing ANYTHING else to your hair
I used to use henna on my hair and on my hands as mehandi designs. What I know is that it releases its red pigment in a relatively acidic mix. Soap being alkaline in nature don't know what happens really. If my one batch of herbal shampoo bar with henna and several other herbs is any indication, it's going to turn a shade of brown, mine was a dark shade as I had hibiscus and a amla infusions as well.
i have used henna in my hair quite a bit. Here is my experience. Henna releases from the powder and is only active for a limited number of hours until the lawsone demises. That is why people normally leave it on for a few hours and rinse. After a while, it won't continue to color your hair.
Now as far as it goes in soap, I would think that the dying action would demise well before the soap cures. I wouldn't imagine that it could stain your skin after it has been sitting in a bar of soap for 6 weeks. The color would still be there. This is all theoretical on my part because I have not used it in soap. I would be interested in knowing how it turns out when your try it.
Has anyone used indigo dye in their soap? I saw some offered by one of the suppliers that I use (cant remember which). Indigo is so fickle with dying hair, that I would imagine that it wouldn't dye skin after being used in soap either.
Edit to add: I don't think that Cassia will color your soap. People use that herb to lessen the "red" of henna. For example, if you wanted strawberry blond. It can also be used to dye white hair blonde.
As far a chemical reactions go-- I don't *think* that the lawsone will be active enough to react to anything. Even if it were active, the type henna that reacts to other chemicals is not pure henna powder, but rather henna mixed with metals or other things to "enhance" it's color or dying abilities. Pure henna should be fine.
The disclaimer is that if you should happen to accidentally dye your hair with henna, it's not coming out for anything! You would probably destroy your hair trying to remove the red, especially if your hair is light colored to begin with. If your hair is dark or black, you won't see the henna anyway because it can't lighten. It only deposits color. Also if you have grey hair, those hairs will dye bright red.
If you accidentally dye your skin, it will wear off naturally.
Henna is a natural product but can be very dangerous. Please research it before using it in soap. Not everyone who might have a severe reaction to it knows it so labelling might not help avoid problems.