What causes dandruff and seborrheic dermatitis?
Some scientists theorize that Malassezia, a type of yeast, may trigger the reaction that creates flakes on the scalp. Malassezia occurs naturally on the body and feeds on sebum secreted by oil-producing glands on the scalp. It’s believed this yeast may leave behind a residue that irritates the scalp. However, there are many cases of dandruff where the yeast is not present, and many scalps with Malassezia but no dandruff. Therefore, the cause of these scalp conditions may extend beyond just the presence of Malassezia. You may notice dandruff worsening in cold, dry weather. But a dry scalp does not necessarily cause excess flaking. Less humidity in the air can lead to a reduced amount of oil on the scalp, which may keep flakes from sticking. Because they are being shed more readily, the flakes become more visible throughout the hair.
