Pictogram 3: Exclamation Mark - Skin Sensitizer

Pictogram 3, the Exclamation Mark pictogram, identifies skin sensitizers. The HCS defines a "sensitizer" as "a chemical that causes a substantial proportion of exposed people or animals to develop an allergic reaction in normal tissue after repeated exposure to the chemical."

When first exposed to skin sensitizers, human or test animal skin shows little or no reaction. However, upon subsequent exposures, a "marked immunological response occurs." Skin sensitizers often cause respiratory sensitization or a general hyper-allergy to some chemicals.

Common skin sensitizers include toluene diisocyanate (used in manufacturing of many products, including coatings and sealants) and nickel compounds. Another commonly occurring skin sensitizer is poison ivy.

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