The appearance of red streaks on the thighs that are neither painful nor itchy may be a sign of stretch marks or pregnancy marks.

This condition is often associated with decreased skin elasticity, and red streaks may appear on the skin when body weight increases or muscle tension rises. It generally doesn't require specific treatment, but some measures can be taken to prevent and improve it, such as maintaining a healthy weight, engaging in moderate exercise, and using moisturizing creams. If the red streaks persist or other symptoms appear, consult a doctor to determine if further treatment is needed.

In addition, skin damage could be caused by overstretching, such as skin cracks resulting from muscle fatigue after strenuous exercise. In this case, it is recommended to avoid excessive force and take care to protect the skin.
For stretch marks or pregnancy marks, applying skincare products containing ingredients such as vitamin E and glycerin can help fade them. At the same time, a balanced diet and moderate exercise can help control weight and increase muscle strength, thereby reducing stress on the skin.