A sensitizing reaction is the result of a response from the body’s immune system to the presence of a chemical or biologic agent. Unlike a toxic chemical, a sensitizing chemical or biologic agent does not cause harm unless there is a reaction from a person’s immune system. One of the common immune system responses that result from a sentizing or allergic reaction is known as “hay fever.” Some chemicals may not be toxic, but can cause sensitizing reactions upon exposure. These are called sensitizers or allergens. Examples of sensitizing chemicals include: latex rubber, metals (i.e., nickel, chromium, beryllium, cobalt, etc.), formaldehyde, isocyanates, toluene, etc. Individuals who react to sensitizers are said to have a sensitivity to a particular allergen. Some chemicals can be toxic and can also be sensitizers. – – http://www.michigan.gov/documents/dleg/reactions_292569_7.pdf