Hello, Your wife has red rashes that appear in large patches on the chest, sides and thighs. They disappear during the course of the day but re-appear every evening towards late afternoon. It can be hives (urticaria) that get triggered due to some irritant. It can also be triggered due to pressure from tight clothing or due to some health condition. She is suggested to stay away from allergens (allergens can be certain food, scented cosmetics, synthetic fabric, soap, moisturizer, etc). She should keep a record of any possible trigger and avoid coming in contact with it. She should wear soft, loose cotton clothes. Taking cold showers is helpful. Applying soothing lotion (Lacto calamine, Soframycin or ointment Hydrocortizone) or cool compresses eases the discomfort. She should avoid scratching. Stress also aggravates hives. Taking non-sedating antihistamines like cetirizine (Zyrtec) or fexofenadine (Allegra) effectively reduces the symptoms. However, chronic hives(urticaria) may lead to severe discomfort, distress and depression. She should get clinically examined by a dermatologist or Allergist as severe allergic reaction can affect the whole body. Sometime, serious breathing difficulties and a loss of consciousness due to hives induced allergy can lead to medical emergency. Get her treated. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician