Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at NSU
Latex is an emulsion of polymer microparticles and it may be natural or synthetic. Natural rubber latex (NRL) is the milky sap of many plants that coagulates on exposure to air.
Natural rubber latex (NRL) being collected from a "wounded" rubber tree. Image source: Wikipedia, public domain.
Latex is most often referred to the cytoplasmic exudate of the Hevea brasiliensis tree, hence the name Hev b allergens. There are more than 250 latex proteins but only 13 proteins have been characterized and designated as Hev b allergens. Skin prick reactivity to Hev b 5, 6, 7 identifies 93% of workers allergic to latex.
Hevea brasiliensis (Rubber Tree). Image source: Wikipedia, public domain.
Use of universal precautions for prevention of blood-borne infections results in exposure of health care workers to latex proteins via latex gloves. Latex has been around for more than a century but its use exploded with the AIDS epidemic in the 1980s. The material was found to strong enough to hold up after hours of surgery and offered the best protection against blood-borne diseases. The use of gloves increased almost 20 times between 1987 and 1997 (from 12 billion pairs to 200 billion).
Latex allergy, a mind map diagram (click to enlarge).
Risk of latex allergy is related to duration of exposure and cumulative use of latex-containing gloves. Corn starch powder in the gloves acts as an airborne vehicle for adherent latex proteins. There is a well-defined dose-response relationship between duration and numbers of gloves used and prevalence of latex sensitization. For example, in a study of dental hygienist students, none of first-year and 10% of 4th-year students were skin test−positive to latex extract.
Approximately 1% of newly hired health care workers are skin prick test−positive to latex. Hand washing disrupts the skin barrier and facilitate sensitization to latex.
Patients affected by latex allergy are especially those who have been exposed through multiple surgeries.
Less than 1% of the general population is sensitized to latex (the scientifically correct name is natural rubber latex). In contrast, 3-17% of health-care workers are sensitized. Latex may trigger allergic reactions in as many as one in 10 people who are exposed to it. By some estimates, 15% of medical workers are allergic to latex.
“Latex allergy” is defined as presence latex−specific IgE with symptoms of IgE-mediated reaction to latex:
- contact urticaria begins minutes after putting on latex gloves in 11% of sensitized workers
- nasal symptoms and wheezing in 15%. Respiratory symptoms are caused by latex proteins that adhere to cornstarch powder and disperse during glove changes.
Cross-reactions with fruits and vegetables
35% of sensitized patients develop allergic reactions to fruits and vegetables that contain proteins that cross-react with latex allergens:
- bell pepper and olive (Hev b 2)
- kiwi, potato (Hev b 5)
- avocado, banana, chestnut (Hev b 6)
- tomato and potato (Hev b 7)
Diagnosis of Latex Allergy
Skin prick test (SPT) with a latex extract is more sensitive and specific than commercial specific IgE immunoassays. However, there are no standardized skin test extracts and the allergists have to prepare the extracts for SPT themselves.
sIgE for latex allergy has much lower sensitivity than previously reported - sensitivity was 35%; specificity 98% (Ann of Allergy, Asthma, Imm, 2012). Sensitivity, specificity, NPV, and PPV of latex-specific IgE assay are 91, 72, 96 and 50%, respectively (http://goo.gl/9gX0F).
An approach to performing a test for immediate hypersensitivity to latex:
1. Prick test with the solution obtained from a soaked latex glove left in saline for one hour. Await 15 minutes.
2. If test 1. is negative, place a wet latex glove on the arm for 15 minutes.
3. If there is no response to test 2., prick through the wet latex glove. Await 15 minutes.
4. Simultaneously draw an ELISA for IgE-anti-latex (ImmunoCAP). Await the results of the ELISA before clearing for the surgical procedure.
Evaluation of patient with possible latex allergy. AAAAI Ask the Expert, 2012.
Avoidance of exposure by a transfer to a latex-safe area in the hospital.
Control of ambient exposure by use of non−natural latex gloves and powder-free gloves by co-workers.
Future dental and surgical procedures should be performed in latex-safe facilities. Patients with history of anaphylaxis should be prescribed emergency epinephrine kits.
Johns Hopkins Hospital announced in January 2008 that it plans to end the use of all latex gloves and almost all latex medical products. It has switched to sterile neoprene and polyisoprene gloves for all surgery despite the fact that the new gloves cost 30-50% more.
Latex allergy is rarely seen in the U.S currently due to the diminished use of latex gloves in health care.
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Multiple choice questions
Chapter 58: Latex Allergy. Allergy and Immunology Review Corner: Chapter 58 of Pediatric Allergy: Principles & Practices, edited by Donald Y.M. Leung, et al.
Latex Allergy. National Institutes of Health.
Latex allergy. Mayo Clinic staff.
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Latex Allergy in OR Workers Decline - from 14.1% in 1998 to 3.9% in 2009. AAAAI 2011 Meeting.
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Latex immunotherapy: state of the art. Guidelines do not consider allergy to latex as indication to desensitization http://goo.gl/j5UaA