Exacerbation of seborrheic dermatitis by topical fluorouracil.

F luorouracil effectively destroys clinical and subclinical actinic keratoses (AKs) by targeting rapidly proliferating cells while sparing normal skin. This effect was initially reported in patients treated with systemic fluorouracil for solid internal malignant neoplasms. Subsequently, topical fluorouracil was demonstrated to clear AKs while minimizing the internal adverse effects associated with systemic treatment. Topical fluorouracil can also produce an intense inflammatory response in areas of seborrheic dermatitis. The purpose of this small, nonrandomized, open-label study was to determine if this inflammatory response could be confirmed prospectively.