As people age, collagen production slows. Collagen is responsible for keeping skin firm, supple and hydrated. Fine lines and wrinkles become more noticeable as people turn 40. Sun exposure and smoking can exacerbate the aging. We all need to use sunscreen, a healthy diet and a smoke-free lifestyle to diminish lines and wrinkles.Dry skin becomes more common when people reach their 40s. Adequate hydration can keep your skin fresh and moist.