While less than 1% of the general population is sensitized to
latex, the U.S. Occupational Safety and Health Administration estimates that 8-12% of health-care workers are sensitized. The major source of workplace exposure is powdered
natural rubber latex (NRL) gloves. NRL is harvested from HEVEA: brasiliensis trees and ammoniated to prevent coagulation resulting in the hydrolysis of the
latex proteins. Prior to use in manufacturing, the
latex is formulated by the addition of multiple chemicals. Thus, human exposure is to a mixture of residual chemicals and hydrolyzed
latex peptides. Clinical manifestations include
irritant contact dermatitis, allergic contact dermatitis (type IV), and type I
immediate hypersensitivity response. Type I (
IgE-mediated) NRL
allergy includes contact
urticaria, systemic
urticaria,
angioedema,
rhinitis,
conjunctivitis,
bronchospasm, and
anaphylaxis. Taking an accurate history, including questions on atopic status,
food allergy, and possible reactions to
latex devices makes diagnosis of type-I
latex allergy possible. To confirm a diagnosis, either in vivo skin prick testing (SPT) or in vitro assays for
latex-specific
IgE are performed. While the SPT is regarded as a primary confirmatory test for
IgE-mediated disease, the absence of a U.S. Food and Drug Administration-licensed HEVEA: brasiliensis
latex extract has restricted its use in diagnosis. Serological tests have, therefore, become critically important as alternative diagnostic tests. Three manufacturers currently have FDA clearance for in vitro tests, to detect NRL-specific
IgE. The commercially available assays may disagree on the antibody status of an individual serum, which may be due to the assay's detecting anti-NRL IgEs to different allergenic NRL
proteins. Sensitized individuals produce specific
IgE antibody to at least 10 potent HEVEA:
allergens, Hev b 1-Hev b 10, each of which differs in its structure, size, and net charge. The relative content and ratios of Hevs in the final
allergen preparation most probably could effect diagnostic accuracy. The Hev
proteins have been cloned and expressed as
recombinant proteins. Sequencing demonstrates both unique
epitopes and sequences commonly found in other
plant proteins. Sequence homology helps to explain the cross reactivity to a variety of foods experienced by
latex allergic individuals. The development of recombinant
allergens provides
reagents that should improve the diagnostic accuracy of tests for
latex allergy. Although clinical and exposure data have been gathered on the factors affecting response in
latex-allergic individuals, less is known regarding the development of sensitization. Coupled with in vitro dermal penetration studies, murine models have been established to investigate the route of exposure in the development of
latex sensitization. Time-course and dose-response studies have shown subcutaneous, intratracheal, or
topical administrations of non-ammoniated
latex proteins to induce
IgE production. Both in vitro penetration and in vivo studies highlight the importance of skin condition in the development of
latex allergy, with enhanced penetration and earlier onset of
IgE production seen with experimentally abraded skin. The diagnosis of
latex allergy is complicated by these variables, which in turn hinder the development of intervention strategies. Further epidemiological assessment is needed to more explicitly define the scope, trends, and demographics of
latex allergy. Diagnostic accuracy can be improved through greater knowledge of
proteins involved in the development of
latex allergy, and better documentation of the presently available diagnostic tests. In vivo and in vitro models can elucidate mechanisms of sensitization and provide an understanding of the role of the exposure route in
latex allergy-associated diseases. Together, these efforts can lead to intervention strategies for reducing
latex allergy in the workplace.