Five cases of severe chronic dermatitis caused by isothiazolinones.

Preservatives used in both industrial and consumer products are well-known and important causes of contact allergy (1). The allergens relevant for this article are the preservatives methylchloroisothiazolinone (MCI) (CAS: 26172-55-4), methylisothiazolinone (MI) (CAS: 268220-4), and benzisothiazolinone (BIT) (CAS: 2634-335). MCI/MI (3:1) has been used as a preservative in cosmetics and household products such as cleaning agents, as well as in industrial products, since the early 1980s. Since the beginning of the millennium, MI has been available on its own for industrial products, and in 2005 its use in cosmetic products was permitted (2). In cosmetics, MCI/MI has been limited to a concentration of 15 ppm, whereas MI alone is limited to 100 ppm. BIT is used in both industrial and household products, such as cleaning agents, paints, polishes, and printing inks (3), but was recently rejected by the Scientific Committee on Consumer Safety for use in cosmetic product, owing to the negative experiences with MI concerning contact allergy (4). From 2009 to 2011, the prevalence of MI contact allergy increased dramatically (5, 6). In 2011, the first 2 cases of airborne allergic contact dermatitis caused by MI in paint were published (7), and it was recently shown that 3 of 4 of MI-allergic patients with relevant exposure to paint had signs of airborne allergic contact dermatitis (6). In 2012, the first case of systemic allergic dermatitis caused by airborne exposure to BIT was published (8). The entity systemic contact dermatitis can present with clinically characteristic features or be clinically indistinguishable from other types of contact dermatitis (9). The clinical features include dermatitis in areas of previous exposure, skin symptoms in