Which of the following is a systemic factor that can influence hair growth?

• A. Hormonal Changes
• B. Scalp Irritation
• C. Hair Styling
• D. Sun Exposure

Answer: (A)

Systemic factors are those that travel through the bloodstream to affect hair follicles throughout the body. Hormonal changes fit this, because hormones circulate widely and regulate the hair growth cycle on a body-wide level. They can influence how long follicles stay in the growth phase and how actively they grow, with different hormones (like thyroid hormones, estrogen, and androgens) impacting hair in various ways. By contrast, scalp irritation is a local condition limited to the skin of the scalp and can cause inflammation or shedding in that area, but it doesn’t send signals through the whole body. Hair styling describes mechanical forces that can damage hair or cause traction but don’t alter systemic hormonal signals. Sun exposure affects the surface environment and can affect hair condition indirectly, but it isn’t a systemic regulator of hair growth.