Son has red nipples

My 4 year old son has a red area around his nipples that is about 1/4 inch in diameter.  It happened gradually over time.   I took him to the doctor and they told me to try hydrocortizone cream but that didn't work.  Now I notice the other nipple starting to do the same thing. Does anyone know what it could be?  i can't think of anything that I changed that he could be allergic to.  I don't notice him itching them either.

[Niquea3]

It sounds like a form of rash. Do you have a history of having hives or eczema? The location of the red area is odd but you can never say how and where the body has reactions. The hydrocortizone may need to be a stronger dose. It could even be the laundry detergent your using. Have you switched lately? I would start using Aveeno products or just anything thats mild soap on his skin until you and your pediatrician can find the solution.
Hope that's helpful and hopefully this doesn't worsen and everything turns out fine for you :)