I used to use henna all the time
Henna always made my hair feel thick and strong after using it. It's a very lovely feeling. The first two times I did it was on virgin hair. The first application turned my hair a super flaming orange-red (my hair is naturally light orange), which oxidized more to a natural looking auburn. The second time I used henna mixed with another herb and it was just as bright at first, but was darker and had purply tones to it.
I don't know why I was so stupid, but I decided to dye my hair very dark, which didn't look natural on me. So, a few damaging processes later, I decided to henna it. It turned my virgin hair a flaming red, and the damaged hair that had grown out, it barely affected. It seems henna does not take well to fried hair. However, I did another application just to the ends and it seemed to work better.
I am not sure whether henna had trouble taking to my hair because it was fried or because of the dye. I am posting this picture to show you the basic idea of it. And by the way, I would check if your henna is pure, otherwise it could very well have a really bad reaction to your dyed strands. Excuse my straightened hair here, but the swept-over browner looking locks are parts I've dyed before.
Dense but fine and delicate 3a hair. Feels like a dandelion without product. Difficulties in getting less puff and more definition when short.
On a mission to grow out after my big chop!