"Sensitizer
Definition
A sensitizer is defined by OSHA 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."
The condition of being sensitized to a chemical is also called chemical hypersensitivity.
Additional Info
Certain chemicals have no immediate health effects. But if you are exposed to them several times, they can make you allergic or sensitive to other chemicals, often quite suddenly. A classic example is formaldehyde (CH2O). Typical reactions to sensitizers can include skin disorders such as eczema and respiratory disorders such as asthma.
Sensitization is an immune response. Therefore, some people may be easily sensitized while others may never be affected. Like any allergic response, a reaction to a sensitizer can be fatal in rare circumstances. You can not predict your reaction to sensitizing chemicals, so treat all sensitizers with great respect and follow proper chemical safety and hygiene procedures.
Books Available
"Toxicology of Chemical Respiratory Hypersensitivity", Hardcover, 172 pages, 1997. Estimated price $150.00. Info and/or order.
"Allergic Hypersensitivities Induced by Chemicals: Recommendations for Prevention", Hardcover, 368 pages 1996. Estimated price $139.95. Info and/or order.
"Chemical Sensitivity: A Guide to Coping With Hypersensitivity Syndrome, Sick Building Syndrome and Other Environmental Illnesses", Paperback, 291 pages, 2008. Estimated price $35.00. Info and/or order.
"Latex Intolerance: Basic Science, Epidemiology, and Clinical Management", Hardcover, 288 pages, 2004. Estimated price $249.95. Info and/or order.
MSDS Relevance
MSDS's should tell you if the material is a potential sensitizer. Avoid working with sensitizers whenever possible. If you must work with them, use a fume hood or other type of engineering control if possible. Always use personal protective equipment such as gloves or even a respirator.
Once you are sensitized to a particular chemical, even minute amounts will cause symptoms. Sensitization is usually a life-long effect.
Further Reading
OSHA standard 1910.1048, Formaldehyde.
ExtoxNet FAQ on chemical hypersensitivity.
WHMIS Quick Facts: Sensitizers, a handy one-page DPDF document you caan post in your workplace.
Selecting The Right Glove: Understanding Latex Allergy And Glove Chemistry at immune.com, an allergy discussion group.
The Health and Safety Authority of Ireland has some a fact sheet titled Guidelines On Occupational Asthma (PDF file).
See also: asthma, irritant, urticaria"
http://www.ilpi.com/msds/ref/sensitizer.html