Diaper rash…it makes a momma want to cry, too. The redness and burning are painful for your little one. And as a mother, you know that what is painful for your child is painful for you, too. What causes diaper rash? The most common cause of diaper rash is chafing caused by a baby being left in a wet and/or dirty diaper too long. The ammonia and other bacteria from urine and stools breaks through the natural dry barrier of your baby’s skin, resulting in chaffing and irritation and burning. Other causes include adverse reactions to scented wipes, laundry soaps and disposable diapers. You might notice a few outbreaks of diaper rash when you begin feeding your baby juices and/or solid foods due to the increased acid in these items.