How are you? What other symptoms are present? Aside from viral infection, this could also be due to irritation, dermatitis or even infection caused by other organisms such as candida or yeast. . Superficial candidal skin infections may appear in areas which are warm and moist including the axilla, neck or groin. These rashes may appear as a red flat rash with sharp scalloped edges with smaller patches called "satellite lesions" nearby. To rule this out, it is best that you have this checked by your doctor or dermatologist for proper evaluation. Treatment will depend on the underlying cause. Take care and do keep us posted.