Hi, Itchy rashes over skin of hands and arms could be due to eczema,allergic hives,atopic dermatitis, tinea corporis etc. The important thing is to diagnose first rather than treatment. You can go to skin specialist for detailed history and inspection of rashes to have a clear diagnosis. You might require topical sunscreen lotion or corticosteroid like beclomethasone, clobetasol or mometasome with antifungal cream like miconazole or itraconazole with antihistamines orally to reduce itching and inflammation. Some time oral antifungal once dosage with prednisolone are also effective. So,you must consult to dermatologist. Thanks