My arms are itchy and i now have big red patches on each arm but no bumps. what can it be?

A fungal infection?: A fungal skin infection often present with ring-shaped lesion with serpentine borders and mild, flaky scales. Can be red/irritated under skin folds such as underarms. Otc lamisil/lotrimin/tinactin all seem to work fine for simple ringworm on body, not scalp/bearded areas. If not better in couple of weeks, or worsens, consult doc for possible alternate diagnosis and proper treatment. Good luck.