This sounds like a very unusual form of nappy rash and I presume that you have tried all of the regular treatments including the usual nappy creams. The possibilities could be one of the following:
This could be due to candida if the baby has recently had antibiotics. Treatment is Nystatin drops by mouth 1ml 4 times a day for 5 days and nystatin cream to the rash 3 times a day. Probiotic drops such as Reuteri must be given for at least 2 weeks.
Another possibility is a zinc or biotin deficiency-this has to be checked by a paeditrician
A third possibility is an allergic reaction known as contact dermatitis to the nappy-change the brand.
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