I'm asking from my boyfriend:

Since my childhood, I'm used to use solid body soap when washing my hair in addition to shampoo. I have oily hair and soap can clean it better than a shampoo.

Recently I'm using a soap which is stronger and cleans oil better and I feel more refreshing! But I realize that it makes my hair thinner and I feel (maybe not) it caused some hairloss over years. Generally speaking, is body soap dangerous for hair and shall we never use it for hairs? Does it cause hairloss?