Seborrheic dermatitis is associated with overgrowth of which organism?

• A. Pityrosporum ovale
• B. Propionibacterium acnes
• C. Staphylococcus aureus
• D. Candida albicans

Answer: (A)

Seborrheic dermatitis is driven by overgrowth of a lipophilic yeast that loves sebum-rich skin. The organism Pityrosporum ovale (now usually called Malassezia species) colonizes oily areas such as the scalp and central face. As it grows, it metabolizes skin lipids into inflammatory byproducts that irritate the skin and trigger an inflammatory response, leading to the characteristic greasy scales and redness.

That’s why topical antifungals that target this yeast are effective. Other organisms listed are associated with different conditions—Propionibacterium acnes with acne, Staphylococcus aureus with various skin infections or atopic changes, and Candida albicans with candidiasis—not seborrheic dermatitis.