Hi and hope you are doing well.
Any skin condition needs to be examined for arriving at a possible diagnosis. Based on the description given by you there are a few possibliities.Conditions like eczema, hives, tinea and psoriasis can cause the appearance of itchy rashes on inner arms and inner groins. In psoriasis there are thick, silvery scales and itchy, dry, inflamed patches that are sometimes painfiul.In Lichen planus there are purplish, itchy, flat-topped bumps on the inner forearm , the lower back, neck and legs .It may also affect mucous membranes, genitals, the scalp or nails. Hives is usually an allergic reaction to food or medicine. During an allergic reaction substances like histamine and other substances are released in the blood stream. Insect bites, medications, pollen all can trigger hives. Take antihistaminic for relief in symptoms. Consult a dermatologist and confirm the diagnosis. Do keep us posted.
Take care and regards!