Latex allergy: How safe are your gloves?
By Kenneth K. Meyer, MD, FACS,
and Donald H. Beezhold, PhD,
A dramatic increase in the incidence of allergic reactions to natural rubber latex followed the introduction of universal precautions in health care settings. These allergic reactions were sparked by the marked increase in glove use and the sudden demand for gloves, which caused supply shortages and the importation of low-quality gloves with high levels of allergen. Fortunately, research has resulted in an understanding of the factors affecting the amounts of allergen, and has encouraged some manufacturers to produce gloves that have both lower antigen levels and are superior surgical tools.
What is latex allergy?
Allergic reactions to natural rubber latex products range from mild contact dermatitis to eczema, rhino-conjunctivitis, asthma, anaphylaxis, and unexplained intraoperative death. Of these, the most common is contact dermatitis, a type-IV delayed hypersensitivity response to the additives used to create a usable product from the natural rubber latex rather than from the latex protein itself. These additives include ammonia, which is added immediately after collection, and other chemical additives (including accelerators and antioxidants used during manufacture to attain the desired characteristics for the final product). Natural rubber latex itself is a plant product produced by specialized cells of the tree Hevea braziliensis, and consists of a complex mixture of polyisoprene, lipids, phospholipids, and proteins. The proteins are the primary allergens causing the more serious systemic reactions. Those reactions are type-I immunologic responses, mediated by IgE antibody, to the proteins remaining in the product. Researchers have determined that hevein preprotein is one of the major protein allergens for health care workers, and a 27kd protein important in spina bifida children. Both the amount of the various proteins in the latex product and the method of manufacture determines the antigenicity of the latex product. Antigenicity is much more likely in products, such as gloves, that are produced by dipping, than in molded products such as syringe plungers and vial stoppers.
Does powder influence the response?
Because powder absorbs the allergens that can then be transferred to the air, surgical instruments, and sutures, to the mucous membranes of patients and the hands of health care workers, glove powder is an important contributor to sensitization and allergic response. Unfortunately, washing powder off of the outer surface of gloves does not reduce the antigenicity of the glove, as surface proteins can be transferred directly by contact with latex alone. During use, sweat dissolves and absorbs some of the protein, transferring it to the skin. Fortunately, the newer methods of coating and latex processing that have made it possible to eliminate starch powder also result in gloves with significantly less protein, and therefore less likelihood of inducing sensitization and allergic reactions. For these reasons, only powder-free gloves should be used in the operating room.
Who is at risk?
Because of their repeated exposure to latex products, especially gloves and glove powders, the incidence of latex allergy in health care workers is much higher than in the general population. The actual reported incidence of latex sensitivity varies from study to study, but has increased from 1980 to the present. The incidence in the general population, which had been less than 1 percent, may be 6 percent; that of dental workers nine to 14 percent, with a 7 to 17 percent incidence in other health professionals. Children with neural tube defects, such as spina bifida, have a 28 percent to 67 percent prevalence. Having had multiple operations is a risk factor because of cumulative exposure to the antigens. Patients with a history of hay fever, eczema, or asthma are also at risk. Because other plants have similar proteins, people with latex sensitization may develop allergies to avocado, banana, potato, tomato, chestnut, or kiwi. Some toy rubber balloons have extremely high levels of allergens, so anyone with a history of allergic reactions to them is highly suspect.
Measuring latex protein
The present tests for latex allergens are the Lowry test, a chemical method based on the binding of chromogenic dye to protein residues, and two essentially equivalent immunochemical tests, the LEAP (Latex ELISA for Antigenic Protein) assay, which uses rabbit IgG, and a human IgE inhibition assay (RAST). Unfortunately for glove users and their patients, the Lowry method, which lacks both sensitivity and specificity, is the national standard as ASTM D5712, even though it is 150 times less sensitive than the immunochemical methods. The immunochemical methods detect proteins at a level of 0.2 µg/gram protein for rabbit IgG and the human IgE, while the lower limit for the modified Lowry method is 28 µg/gram protein.
Are all gloves equal?
No. There is significant variability in the amount of allergens in different brands of latex gloves. Allergen levels are considerably lower in powder-free gloves as a result of the washing and chlorination steps involved in the manufacture of powderless gloves. They are significantly higher in gloves that use starch powder as the donning medium. Powdered gloves have a range of <20 to 1039 µg/g (median 191) by the Lowry test with precipitation and less than 0.1 to 293 µg/g (median 26) by the LEAP assay. Natural latex powder-free gloves have a range of less than 20 to 108 µg/g (median 33) by the Lowry test and less than 0.1 to 21 µg/g (median, 0.9) by the LEAP assay. Gloves labeled as hypoallergenic range from less than 28 to 192 µg/g protein by the Lowry method and 5.9 to 49 µg/g by LEAP. Highest of all are those gloves labeled orthopaedic, which have levels of 350 to 439 µg/g by the Lowry test and 89 to 115 µg/g by LEAP.
Is variation significant?
Yes. If patients with documented latex allergy are tested by the skin-prick test, more than 68 percent test positive to regular powdered gloves; and if the test is performed with only those gloves that test at the 50 µg/g detection of the modified Lowry test, 58 percent will react. For gloves that test below the 0.2 µg/g lower limit of protein detection by the LEAP assay, only 11 percent of latex allergic patients will have a positive skin-prick test. Laboratory tests cannot determine that no protein is present in the glove, and no manufacturer can honestly claim their latex gloves to be protein-free just because protein is undetectable by tests. Clearly, gloves with undetectable protein by the immunological methods have a significantly less likelihood of causing reaction than those tested by the Lowry method.
Another advantage of low protein, powder-free gloves is that they hydrate more slowly and thus maintain their tensile and tactile properties as well as their resistance to chemical and viral transfer.
Treating latex allergy
If the reaction is contact dermatitis, patients should be tested by patch testing, as the allergen may be a latex additive rather than latex protein. Changing to a different glove may solve the problem. For some surgeons or other health care workers, a glove liner, especially one made from DemithaneTM, may be an effective treatment for contact dermatitis. The only treatment for type-I reactions, mediated through IgE, is to avoid exposure to latex entirely. Individuals with atopy, food allergies, asthma, and a history of multiple surgical procedures (especially if they have had adverse intraoperative events) should be tested preoperatively and be placed in a latex-safe environment. It is easier to create such an environment if the entire hospital uses only powder-free gloves—thereby avoiding the problem of aerosolization of latex proteins.
Reducing the risk
Surgeons should insist on powder-free gloves and should know the protein content of the surgical and examination gloves they use. Because of the inadequacy of the Lowry test, manufacturers should be asked the results from the LEAP or RAST inhibition assay. The ideal glove is one with less than 1 µg/gm by the LEAP test and one to 14 allergen units/ml on the RAST inhibition assay. One should at least insist the gloves be less than 10 by LEAP assay or less than 100 allergen units on the RAST. It may not be easy to effect a change, as the ideal gloves tend to cost more, and business managers who do not understand the costs of adverse reactions and consider only price may be difficult to convince.
- Beck WC, Beezhold DH: Starch glove powder should follow talc into limbo. J Am Coll Surg, 178:185–186, 1994.
- Beezhold DH, Zehr B, Kostyal D: Prevention of latex allergen transfer by glove liners. Guthrie J, 66:15–19, 1997.
- Beezhold DH, Sussman GL: Determining the allergenic potential of latex gloves: Surg Services Manag, 3:35–47, 1997.
- Hammann CP: Natural rubber latex protein sensitivity in review: Am J of Con Derm, 4:4–21, 1993.
- Sussman GL, Beezhold DH: Allergy to latex rubber: Ann Int Med, 122:43–46, 1995.
July 1997 Volume 82 Number 7
American College of Surgeons
Reproduced here with permission.