I was critically ill as a child and as a result, I developed a lifelong problem with yeast because of all of the antibiotics I took for so many years. I take a very good quality acidophilus every day to help to control the yeast. What you see on his skin, is likely just a topical expression of what's going on inside, especially if his PEG itself smells like yeast. My Uncle takes acidophilus everyday because of the variety of medications he takes for his heart condition and two stents. Aunt Rosemary took it for a while after her glossectomy because she had yeast in her mouth from the seventeen medications they gave her in the hospital. It's very easy to knock someone's yeast level out of balance, and while I am a life long user of Diflucan (I take 50mg. every night), the acidophilus will keep his yeast levels in check- naturally. You can mix it with water and pour it into the tube. I'll bet you that rash will disappear quickly.