Background: Allergy to natural rubber latex is increasingly common and serious in children and adults. Latex is the milky fluid derived from the lactiferous cells of the rubber tree, Hevea brasiliensis. It is composed primarily of cis-1,4-polyisoprene, a benign organic polymer that confers most of the strength and elasticity of latex. It also contains a large variety of sugars, lipids, nucleic acids, and highly allergenic proteins.
More than 200 polypeptides have been isolated from latex. Latex proteins vary in their allergenic potential. Protein content varies with harvest location and manufacturing process. Basic knowledge of the manufacturing processes aids in understanding the medical problems related to latex exposure.
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Freshly harvested latex from Malaysia, Indonesia, Thailand, and South America is treated with ammonia and other preservatives to prevent deterioration during transport to factories. Latex is treated with antioxidants and accelerators, including thiurams, carbamates, and mercaptobenzothiazoles. It is then shaped into the desired object and vulcanized to produce disulfide cross-linking of latex molecules.
After being dried and rinsed to reduce proteins and impurities, the product frequently is dry-lubricated with cornstarch or talc powder. Powder particles rapidly adsorb residual latex proteins; other proteins remain in soluble form on the surface of finished products.
Latex is ubiquitous in modern society and particularly in health care. William Halstead first used latex surgical gloves in 1890. Latex has been used in a myriad of medical devices for decades. In the late 1980s, however, its use skyrocketed as latex gloves were widely recommended to prevent transmission of blood-borne pathogens, including the human immunodeficiency virus (HIV). Billions of pairs of medical gloves are imported to the United States annually, often as powdered, nonsterile examination gloves.
In the 1980s and 1990s, heightened demand for latex to manufacture gloves and other objects resulted in hundreds of new, poorly regulated latex factories in tropical countries. The incidence of minor and serious allergic reactions to latex began to rise rapidly among patients and health care workers (HCWs). Latex sensitization can occur after skin or mucosal contact, after peritoneal contact during surgery, and possibly after inhalation of aerosolized particles with latex on their surfaces.
Pathophysiology: Latex exposure is associated with three clinical syndromes.
The first syndrome is irritant dermatitis. It is a result of mechanical disruption of the skin due to the rubbing of gloves and accounts for the majority of latex-induced local skin rashes. It is not immune mediated, is not associated with allergic complications, and is not the subject of this article. It may be confused with Type IV hypersensitivity. Any chronic hand dermatitis in HCWs raises the risk of nosocomial infections, including blood-borne pathogens.
The second syndrome is a delayed (type IV) hypersensitivity reaction, resulting in a typical contact dermatitis. Symptoms usually develop within 24-48 hours of cutaneous or mucous membrane exposure to latex in a sensitized person. The primary allergens are residual accelerators and antioxidants left from the original manufacturing process. Langerhans cells process the antigens and present them to cutaneous T cells. Multiple objects can cause sensitization, but the most common sources in this country are probably examination gloves for adults and shoe soles for children. Type IV hypersensitivity is more common in atopic individuals. The dermatitis may predispose patients to further sensitizations or infections.