Brief Answer: Nystatin Detailed Answer: Hello. Thank you for your question. Although anything can happen, allergy to Nystatin is very unusual. I think it is more likely that in addition to the fungus that caused the rash, there is also some bacteria involved. as the Nystatin begins to eradicate the fungal component, the bacterial component worsens the rash. I don't have the benefit of being able to view the rash with my own eyes. However, I believe and over-the-counter antibiotic ointment, such as Bacitracin, apllied three times per day, will be beneficial. If the rash continues to worsen over the next 2-3 days, I recommend consulting with your doctor.

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