Itchy Scalp, Increased Hair Fall, Using Hair 4 Topical Solution, Used Lo'real Casting Hair Color. What Is The Cause?

hi, I am using Hair 4 u topical solution for the past 3 weeks, initially it showed good result, as in I saw relatively less hair fall. But for the past few days my scalp is very itchy and the hair fall has again increased. I color my hair with Loreal Casting - no ammonia hair colour, is it because of the hair colour that I am feeling itchy. Please advice, as my problem is grave.