I don't know if this rash with respond, but my duaghter used to get BAD diaper rashes sometimes, and her butt weould be RAW, the BEST STUFF we found and have used forever more was called "Triple Paste" it comes in a big white and blue round tub, and a little goes a long way. It would make a vast improvement in just one application. They sell it at Target and WalMart and Walgreens. I swear by the stuff and I give it as baby shower gifts, along with my homemade wipes recipe.
Maybe you should try homemade wipes, too? I swear they made my kids much less irritated down there, and helped keep diaper rash away. Here is the recipe:
Cut a paper towel roll in half (plain white Viva or Bounty towels work best) to make 2 shorter rolls
put in an airtight container with a lid....Rubbermaid makes a 3 qt. canister that is just right, you can get at WalMart - or a washed out large plastic coffee can with lid works too
get a measuring cup and fill with 2 cups warm tap water, add in 2 Tbsp Baby wash, and 1 Tbsp Baby Oil ( whatever brand you already use for baths)....mix up with a wisk or fork
Pour liquid over towels in container, then pull out cardboard tube in the middle to start the wipes! Keep covered, lasts for weeks, depending on how many diapers you change per day!
Good Luck!
Jessie