Henna treatments make your hair darker over time? Based on Curly Nikki's hair.

I was looking over Curly Nikki's henna page on her website and she mentioned that over several uses of henna treatments, it made her hair including her highlights, darker (understanding the fact of the auburn hue in certain light). Has anyone ever experience this as well?

Yep, the henna has darkened my hair. (the auburn tones have gotten darker as well) If you don't want your hair to get any darker, you can apply the Henna to your new growth only.

I find that true with my hair as well and it darkens over time. On the day of the application, my hair is very firey, but after 2-3 days it darkens.