Rash on the forearm

38-year-old high school teacher came to clinic complaining of rashes on his forearm, arm and upper chest. Rash appeared gradually four months ago, is intermittent, getting worse. Skin lesions are not painful but are associated with exercise, it appears after a workout and lasts for a few hours, and then it resolves. He is not taking any medication or using new skin supplements, and he denied fever, weight loss, joint pain, cold or heat intolerance, abdominal pain or any bone pain. He also denied having a familiar history of skin, thyroid or rheumatologic disease. On physical examination, skin temperature was normal; on the right forearm, raised erythematous plaques that are intensely pruritic was noticed, as is shown in the image below. Which of the following is the most likely diagnosis,