Tea tree oil may help some people with dandruff, but the evidence is too limited to call Melaleuca Alternifolia Leaf Oil a dependable choice for seborrheic dermatitis. One controlled study found that a shampoo containing 5% tea tree oil improved dandruff scores more than its placebo shampoo over four weeks. That result belongs to one finished shampoo, not every product that lists tea tree oil.

Tea tree oil can also cause burning, redness, irritation or allergic reactions, which matters when seb derm skin is already inflamed. The trial did not report adverse effects, but it was not large enough to rule out reactions more broadly. Avoid applying undiluted oil, and stop using a product if it consistently stings or worsens your skin.