We have used purex free and clear for over 8 years.
We have never had a diaper rash and I have sensitive skinned kiddos.
We also have some of the hardest water in the country. We use one full cap for each load and one extra rinse. Every month or so they soak for 2 hours with plain white vinegar.
The harder the water the more soap, soft water less soap.
Katie, mom to Olivia (97), Veda (98), Franky (2004), Wendy (2005), JoHannah (2007), Thea (2009) and Sunny (2011)