The rash is not touching/under the diaper at all? If it is where the leg elastics touch it could be a detergent sensitivity (my dd had this around her thighs too from detergent buildup - I rinsed the diapers on hot a few times and she's fine now)
Lisa ~ WAH, bf-ing, cs-ing, hb-ing, vegan mama to Anna (09/07) and expecting #2 in March 2012!
I have the same problem, and haven't been able to figure it out. But we use exclusively prefolds, and Charlie's, and I kind of thought that both these things would make buildup less likely....? I only use wool soakers with no elastic, so it's not that...
Pregnant and/or breastfeeding since May, 2004, with dd6, ds4, and dd born 9/11. We .