The surface area of a head of hair is huge. Hair that is 16 inches long has a surface area of approximately 40 sq. feet – this is about the size of a large bed and a much larger surface area than that of the skin.
Hair picks up dirt and grime from the atmosphere, even more so for those that live in a city. Any dirt, dust, or pollution in the air can be damaging, causing hair to become dry, dull, and brittle.
The easy solution – wash and condition hair frequently (every day, or every other day at least).