My son never had a rash as a newborn, but recently he has had a recurring rash along with extremely foul smelling stool. He is almost 16 months, weighs about 23 pounds and is about 30 inches long. He was breastfed until 5 months and then I gave him both breast milk and formula until 7 months. From 7-12 months he had only formula. I put him on whole milk at 1 yr. As an infant he had constant reflux and threw up at least 5-7 times a day. The reflux slowly got better and was completely gone by 10-11 months, but during that time we never noticed anything unusual about his stool, nor did he ever develop a rash. The horrible smell and rash didnt start until he was about 11 months. Sometimes the smell is so bad his pants or shorts will smell even though the stool has not leaked out. The stool is sometimes on the watery side, but not too loose. What can be causing this?