Dermatite allergica da contatto a metilene-4,4′-difenildiisocianato in una studentessa di chimica

Methylene-4,4′-diphenyldiisocyanate (MDI) is an aromatic isocyanate commonly used to prepare polyurethanes which are chemical compounds formed by condensation or adduction between isocyanates and polyols. Isocyanates are known as sensitizers of the respiratory tract, skin and eyes. They are strong skin irritants. A case of airborne allergic contact dermatitis from MDI in a 26-year-old female student, who consulted us for an erythematous and vesicular dermatitis of the forearms and face, is reported. As she had to prepare a thesis in chemistry, she attended a laboratory where she had to mix a polyol with an isocyanate, Voranate® M600 SH Polymeric MDI. After a few months of work, a fire destroyed part of the laboratory, including the fumes-hoods, but she decided to carry on her work in spite of the lack of adequate protection. The patch testing showed positive reaction only to MDI 0.1% pet. As she referred to us she had never moulded other isocyanates before, including MDI, she had probably become occupationally sensitized to MDI contained in Voranate® M600 SH Polymeric MDI. This confirms that isocyanates are strong skin sensitizers which necessitate preventive measures.