Solid shampoo is a more natural way to wash your hair. If you are using solid shampoo for the first time, your hair may need time to adjust. If you experience excessive oily scalp or residue on the hair, a vinegar rinse will bring it back to normal. The adjustment period is usually temporary and lasts a month or so, but it’s worth it! Solid shampoo will make your hair grow faster, thicker and can also assist with dandruff, psoriasis, oily/dry scalp.