Not that I can tell. Check out the BKT support thread and it'll answer most of your questions. I've retained 3 inches in the past 4 months, so I know it has had no adverse effects on my hair. Just finished a treatment about an hour ago and my hair just looks betterer and betterer.
I've read that not only are there not problems with keeping in moisture, it has helped people keep moisture in their hair. And no issues with DC's not working either......just don't ask me to give a scientific explanation on that .
Idk, but it seems like that might be overkill on your strands having the BKT coatings on your hair and then the henna on top of that. It seems they serve a similar purpose so I would just choose one or the other.....or wait until the BKT wears off to do the henna and maybe alternate the 2 treatments.