OH YES! I have heard of this and it works GREAT! You just mix some Maalox with some baby powder until it forms a paste and slap that on their rear end over the rash. Its awesome!! Better than anything else I've tried before for a really bad rash. Hope it helps your little one!
I use Milk of Magnesia on sunburn and it is GREAT! It takes the burn away and is cool and soothing. Sometimes you have to put it on a couple of times, but it feels really good. I would say to try it and see. Put some on a cotton ball and use on affected areas. The only thing is if it dries on, you will have to use a warm wash cloth to remove it. If you try it, let me know if it works.
Actually milk of magnesia and cornstarch baby powder was the ONLY thing that worked on my youngest- she was born with what I thought was a horrible diaper rash- turned out she had thrush so bad it showed up there! I would put on the milk and then put the powder on top- cleared it up in a matter of days (and I mean it was a horrible- raw mess!).