Ok this will sound like the dumbest answer to this inquiry, but it worked. years ago I developed alopecia in big round spots, looked like an alien grabbed my head in the middle of the night. I lost all of the hair in the spots. When it grew back it was whiteish gray. I found some people online who were talking about the wonders of using onion juice as a shampoo before your normal washing. Here's how it works:

Grind up an onion, turn it into a mush (it will be COLD) DO NOT GET IN YOUR EYES!! Apply generously Use It ALL... and wrap the head in a towel (tried turban hair wraps and shower caps, but only the towel kept it out of our eyes.) Leave on for at least 45 minutes, then wash out using your normal shampoo. Will take several washings to get smell out but recommended to do twice a week

It not only grew my hair back, it darkened the gray spots and made the hair springy and it shines. My wife's hair is naturally blonde with white and she used to dye it auburn, and it never seemed to grow past her shoulders. When she did this her hair got thicker, springier, and it shined like it was metallic. She had gold silver and copper hair for a while. It was wild. It also accelerated the growth.

after it grew back, we only need to do it once a month now to have the same results. The hair will be VERY clean and able to absorb better the conditioner.

BONUS*** Just a theory, but it might help to match the onion color with the hair color (White onion for gray, Yellow for blonde, red for brown/black) It did add a slight tinge of color, but not in a bad way.

Hope this helps, feel free to ask if you have anymore questions and let us know if it helps. Always best to try the natural first right?