Hello I currently use Fairy as it is decent and non allergenic but it does seem to fade my black clothes - this is a problem with black patterned fabrics. I wash at 40C and dry inside out but they do fade. What is the best washing powder to prevent fading, particularly in natural fabrics?
I don't think there is just one. I use the standard Persil one with optical brighteners (which is probably in the Fairy and causing the colours to fade) for whites, and Persil colour for colours and a delicates liquid for my wool and hand wash cycle.
I also wash at 30 degrees apart from the odd 60 degree when the towels and sheets and workout gear need a bit extra, but only when the fabric can stand it.