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Information on Latex Protein Allergy and Gloves The following text on Latex Protein Allergy is taken from a paper written by the Rubber Research Institute of Malaysia (RRIM) in January, 1998. This paper is an excellent reference for all glove users wanting to learn more about latex protein allergy. It also addresses some of the misinformation in the news media on the subject. Shown here are excerpts from this paper. The complete text can be found on the Internet within the the Rubber Research Institute of Malaysia Web site. Look for it within the Latex Protein Allergy Links section at http://www.lgm.gov.my.Latex Protein Allergy and Your Gloves This document is written to redress the negative and often misinformed comments in the news media and on the Internet concerning latex protein allergy. We hope to present a more balanced account of the subject by giving full weight not only to the problem, but also to the efforts which have been and are being made to improve the situation. The latex protein allergy affecting some users of latex products has caused great concern to both the medical profession and the latex product industry. The problem appears to have been triggered by the sudden upsurge in the use of latex gloves due to the AIDS scare in the late 1980s, when some gloves with high levels of allergenic proteins were produced. To address the problem, a great deal of research has been carried out in Malaysia and other manufacturing countries, as well as in consumer countries in the West. While studies in Europe and USA have been largely concerned with the development of suitable diagnostic tests, efforts have been made in Malaysia to further improve quality of the products. Intensive R&D by the Rubber Research Institute of Malaysia (RRIM) has enabled Malaysian glove factories to produce gloves with superior qualities with low protein / allergen content. The use of such gloves will help to reduce the possibility of further sensitization. Back to top
What is Latex Allergy?
The three types of adverse reactions associated with latex gloves affecting some users are shown in Table 1.
Table 1: Reaction Types Associated with Latex Gloves
While the irritant contact dermatitis and Type IV hypersensitivity have been known for many years, that of Type I hypersensitivity emerged only in the late 1980s. Type I hypersensitivity is not only caused by natural rubber (NR) latex products, but is frequently caused in some individuals by penicillin, other antibiotics, wasp and bee stings, and even some foods such as fruits and peanuts. Back to top
Who is at Risk?
Of the three types, Type I hypersensitivity is considered to be the most serious one. The prevalence of this type of allergy among the general population is not exactly known, but estimates of less than 1% have been given. A number of high risk groups have been identified, and their incidences of occurrence as diagnosed by skin testing, have been reported (Table 2).
Table 2: Prevalence of various potential high-risk groups
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Diagnosis of Latex Protein Allergy.
A complete medical history is an important indicator. A skin prick test is a sensitive and simple test for the allergy. It is in fact considered to be the "golden standard" test, although it could sometimes cause allergic reaction, if not properly performed. It involves pricking the skin, usually on the forearm, through a drop of test liquid containing the allergenic materials. It should only be carried out at medical centers with staff who are experienced and equipped to handle severe reactions. Swelling or redness at the test site indicates a positive reaction within minutes of application.
Blood tests can also be conducted by measuring the specific IgE antibodies in the serum using technique such as the
radio-allergosorbent test (RAST). However, such tests lack high sensitivity of the clinical skin test. As with other medical tests, no single test result is one hundred percent accurate.
Once a positive diagnosis is determined, then the most sensible remedy is avoidance of NR latex proteins. It must be emphasized that proper diagnosis should be done and all hypersensitive persons should be identified so that they would not continue to expose themselves to the allergens to which they are sensitive. Otherwise, very unpleasant or serious consequences could result.
What are Residual Extractable Proteins? If latex is ultracentrifuged, the latex system can be separated into three fractions. The least dense upper fraction of rubber hydrocarbon particles forms the main ingredient of all rubber products. The other two fractions are usually removed to a great extent during processing. NR latex contains about 1% of total proteins. About 3/4 is in the non-rubber phase of the latex, and it is water-soluble. When processed into latex concentrate, considerable amounts of these soluble proteins are removed. Further conversion of latex into a film, such as gloves, condoms or balloons, removes more of the soluble proteins, during leaching and washing steps, so that the remaining levels are very low. These residual proteins in the latex products are those which are implicated in the allergy. Not all proteins in the residual extractable fraction cause the allergic reaction. So far, about nine of the potential allergens presents in the latex15 have been identified. This subject, together with the study of changes in proteins from latex to the product, is being intensively investigated. Back to top
Allergic potential of latex gloves
Since the amount of residual extractable proteins present in latex products prepared from the same latex concentrate can vary, depending on the processing conditions they are subjected during manufacturing, not all gloves have the same amount of residual extractable proteins. For example, gloves that have been subjected to more thorough leaching during processing will have less extractable proteins then those that have not, although the latex used for both may have originated from the same source of supply. A sensitive and accurate method is needed to evaluate the allergic potential of these products. However, presently there is no universally agreed method for doing so. In fact, the tests adopted currently are of two main types: (1) measurement of total extractable proteins, and (2) assessment of allergenicity or allergen content.
Generally for routine testing, the much simpler and faster total extractable protein methods are used. As mentioned earlier, these tests are not specific to latex allergens. Therefore, for meaningful indication of the allergic potential, it is important that the extractable protein (EP) values produced, by whichever test used, should show significant correlation with the allergic response or the allergen contents of the samples analyzed. Such relationships have been demonstrated by the EP values generated from the RRIM modified Lowry test making this a very useful procedure.
Values by the RRIM modified Lowry (EPRRIM) have been reported to be very well correlated with those by ASTM
(EPASTM).
EP Levels of Gloves and Other Latex Products? Extractable protein content of latex gloves has been found to vary from as low as less than 20 ug/g of glove to as high as more than 1000 ug/g (as measured by the RRIM modified Lowry test). While the well-leached powdered gloves and the powder-free gloves usually have low EP contents, those of the poorly leached gloves have high EP contents. On the other hand, other latex products such as condoms, latex thread, balloon bags and teats have narrower EP range varying from less than 20 ug/g to about 200 ug/g. Chlorinated products such as catheters and most powder-free gloves always have very low EP values of below 100 ug/g. Are There "Safe" EP Levels? For already sensitized and hypersensitive individuals, the only course is one of avoidance of latex. Some individuals who experience allergic reactions to latex proteins also show cross-reactive responses to proteins in foods (such as various fruits and nuts). These foods should also be avoided. For the rest of the population, threshold level for sensitization is not known, but it is possible to obtain indication on extractable protein levels of low risk by identifying levels at which a great number of latex hypersensitive individuals do not react. The RRIM, in collaboration with Dr. K. Turjanmaa of the Department of Dermatology, Tampere University in Finland, has shown20 that when latex hypersensitive subjects were skin tested with latex gloves of varying content of EPRRIM, about 60% of them indicated no allergic response at levels less than 400 ug/g. Up to 100% negative responses were observed at EPRRIM lower than about 100 ug/g in this study. Subsequent collaborative work with Dr. T. Palosuo of the Department of Immunobiology, Institute of National Public Health in Helsinki, using ELISA-inhibition technique (which has been validated by the skin prick test) confirmed that gloves with EPRRIM of about 100 ug/g and less also have very low allergen contents21. These findings have provided very useful guidelines for not only the manufacturing of low protein/low allergenicity gloves, but also for selection of gloves by the users. The Food and Drug Administration (FDA) of the USA has allowed "Low Protein Labeling" claim for the 510k submission by glove manufacturers since March 1995. However, no maximum EP levels have yet been specified, although claims below 50 ug/g (sensitivity limit of the ASTM modified Lowry test) is not permitted. Back to top
Production of Low Protein Gloves.
Much effort has been made by many manufacturers in Malaysia to reduce the EP levels of their products. Approaches taken include:
Adoption of improved leaching protocols during processing, as recommended by RRIM22
Use of low protein lattices
Chlorination23
Polymer coating
The RRIM glove surveys revealed that EP levels decrease steadily from 1992 to 1996. Gloves with low EP content and low allergen level are now available, especially in Malaysia.
Does Powder in Gloves Enhance the Allergy Reaction?
Powder is used in the manufacturing of gloves to facilitate easy donning as well as to prevent the glove surfaces from sticking together. The cornstarch powder used is, by itself, not an allergen. However, it is believed that powder could absorb some of the extractable proteins from gloves, becomes airborne, and inhalation of the aerosolized powder could cause sensitization. However, this mode of sensitization is a subject of debate.
It is often found that powder-free gloves have much lower extractable protein levels because of the manufacturing processes used in the production.
Nevertheless, it may be interesting to note that absorption of allergenic proteins by powder from gloves can only be viewed as serious if the gloves concerned have high EP contents. Absorption should be insignificant if the gloves are of low EP contents.
Selection of Gloves for Safe Use.
The main function of wearing gloves is to protect the wearer against contamination of infectious materials particularly viruses, bacteria, infected blood and body fluids. Thus, the single most important criterion in glove selection is barrier protection, as defined by all users, including physicians, dentists, medical and non-medical workers and researchers.
The next most important criterion is strength, fit and comfort, that is, the ability for the glove to stretch, remain soft, and conform to the hand. Other important requirements include tactile sensitivity, the ability to grip thing well, and the ease of donning. It is widely acknowledged that NR latex gloves are unsurpassed in their range of properties25. Hence, selection of glove for safe use should be one of NR with the following properties:
Good barrier performance
Strength
Fit and comfort
Tactile sensitivity
Good grip
Easy donning
Low extractable protein content
Minimum level of chemical residues
However, for the latex sensitive individuals, selection should also be based on similar requirements, except that the gloves will have to be protein-free. This means the use of gloves made of non-NR materials should be the choice for them, although it may be difficult to find an alternative to latex that matches it in terms of its superior physical properties26.
How do Non-Latex Gloves Perform as Compared to Natural Rubber Latex Gloves?
Although non-latex gloves may be protein-free, it must however, be remembered that the most important function of gloves is to provide barrier protection for the users to avoid contact with infectious materials. Thus far, latex gloves have been proven to have excellent barrier protective capability, and other superior physical properties.
On the other hand, non-latex synthetic gloves are generally known to lack the comfort and fit, as well as lower strength and endurance as compared to the latex gloves. Above all, their barrier properties are often inferior to those of latex gloves, as demonstrated in the case of vinyl gloves 27, 28.
Furthermore, it may be emphasized that non-latex gloves are not free from eliciting allergic reaction in some users. The fact that the same chemical compounding chemicals are used in their processing, they can also cause Type IV hypersensitivity. Therefore, unless one is latex sensitive, the glove of choice should clearly be that of latex.
Maximum Performance of Latex Gloves.
For maximum performance of latex gloves, care should be taken to ensure proper storage and correct usage of the products. Rubber tends to deteriorate with prolonged aging, especially in warm climate. Therefore, they should be kept in containers and stored in a cool dry place. Storage for an unnecessarily long period is not recommended. As soon as signs of deterioration appear (e.g. tackiness, brittleness, acrid odor), the gloves should be destroyed.
Correct usage of latex gloves is also important. For long operational procedures, there is a need to change gloves at regular intervals to prevent accumulation of fluids in the gloves. For challenging procedures, which could sometimes result in holes and cuts, the use of double gloving is recommended to provide maximum protection. The contact with oil-based antiseptics, phenols and their derivatives, petroleum-based grease, kerosene and other related organic compounds, should be avoided.
References.
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