What effect does sebum have on hair?

Sebum, which is the natural oil produced by sebaceous glands in the skin, plays a vital role in maintaining the health and condition of hair. One of its primary functions is to provide moisture. Sebum coats the hair strands, creating a protective layer that helps to prevent moisture loss from the hair shaft. This moisture retention is crucial as it keeps hair hydrated and can lead to a smoother texture, reducing issues like brittleness and dryness.

While sebum does contribute to the hair's overall health, it does not inherently add color, increase thickness, or cause frizz. Therefore, the answer emphasizing its moisturizing properties correctly identifies its most significant effect on hair.