This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
[{'content': 'Which of the following is the most common side effect of Isotretinoin used for acne vulgaris? \nSelect and explain. \nA. Facial erythema, B. Xerosis, C. Hair loss, D. Cheilitis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Cheilitis is the most common side effect of isotretinoin. Ref: Rook Textbook of Dermatology, 8th edition, Page 42.64', 'role': 'assistant'}]