Can lactose intolerance cause nappy rash? DD (2 years) loves her milk, but the more she drinks the worse her bottom gets. We're trying soy milk for the first time this week. Be interesting to see if her bottom improves. Just wondering if anyone else has the same problem with cows milk? Also wondering if there's anything I should know about which type of soy milk to choose. We're using a calcium-fortified brand.