You are suffering from what Dermatologist call urticaria. Common causes are food allergy, infection or drugs taken for some condition. It presents with itching resulting in formation of red rashes which we call hives or wheals. Although in most cases cause remains unknown in spite of a thorough search. It can be treated with medicines so that you do not get any new hives. The treatment should be prolonged until it resolves which usually takes 1 to 6 months. Please contact me through online consult option for further details and treatment..

It looks like pressure urticaria. In this condition, the person will have itchy bumpy rash on the skin where pressure is applied. Probably pressure over the shoulder area of your wife is causing this problem . It can be easily treated by anti allergic tablets.  Also try to avoid pressure on any part of the body