Oral involvement of cutaneous T-cell lymphoma.

Methylisothiazolinone (MI) is commonly used as a preservative in personal care products and is a frequent cause of allergic contact dermatitis. We present a patient with allergic contact dermatitis caused by MI in hair care products and discuss this allergen to bring attention to this common cause of contact dermatitis, and to highlight its frequent use in hair care products. If allergy to MI is suspected, testing should be performed to this individual preservative, as testing solely for the combination preservative, methylisothiazolinone/methylchloroisothiazolinone (Kathon CG®), may miss many cases of MI allergy.