Selecting The Right Glove:
Understanding Latex Allergy And Glove Chemistry
By Edward Lehrman, MD (written ~August 29, 1996)
Over the past few years, there has been an increasing incidence of allergic reactions among
health care workers to latex medical gloves. Current estimates on the prevalence
of latex allergy among health care workers range as high as 17%. This is thought
to be largely due to the institution of universal precautions in response to the
AIDS epidemic, and the resultant dramatic increase in glove usage. A large body
of literature on this subject has built up in the allergy, immunology, and
nursing journals, but there have been relatively few publications in the
surgical literature, so many surgeons and surgical subspecialists remain
relatively ignorant in this area. This review will summarize the most important
findings from this literature from the point of view of the glove user (the
surgeon and nurse). A major theme of this monograph is that a latex glove, like
all medical devices, has benefits as well as risks. There are potential side
effects from this device, and the surgeon needs to consider these in making his
or her choice of surgical glove. I hope to cover: You should understand what it is that you are putting against your skin. It
is important to consider the risk of allergic sensitization when selecting
gloves rather than just choosing the lowest cost item available, or simply
relying on the hospital purchasing department to make the appropriate choice for
you. I am going to focus on sterile gloves for use in surgery, but remember that
non-sterile examination gloves for use in the office are important to evaluate
as well. What glove characteristics should we look for? There are several important considerations. First, gloves offer barrier
protection both for the health care worker and the patient to guard against
contact with blood, other body fluids, and microorganisms. Latex has been in use
for about 100 years, and has proven barrier protective capability. In a series
of studies, Korniewicz and co-workers9,10,11 have shown that vinyl
gloves have higher leakage rates than latex (less barrier effectiveness), and
are therefore less suitable for surgery. They reported that although both vinyl
and latex examination gloves provide protection to the user, latex gloves
maintain their integrity longer under in-use conditions. The barrier
effectiveness of synthetic rubber gloves is not as well established at this time
as for latex. 18 Second, a glove needs to be comfortable. One should be able to don it (slip
one’s hand into it) easily, and then be able to perform surgery as if you
weren’t even wearing a glove at all. Again, latex excels - the synthetic
materials are frequently stiffer than latex, and less comfortable to wear. Third, cost is important. Latex gloves are usually less expensive than
synthetic rubber gloves. So latex has substantial benefits as a material for surgical gloves. What are
the risks? Latex Allergy A latex glove contains natural latex, cornstarch powder frequently (added to
help the surgeon don the glove), and numerous chemicals, some of which will be
discussed below. These are foreign matter, and the human immune system sometimes
responds. There are 3 major types of reactions. There are several groups of people known to be at increased risk for latex
allergy: patients who have had multiple hospitalizations and been exposed
numerous times to latex medical products (especially patients with spina
bifida), health care workers, and workers in the rubber industry. Current
estimates are that 8-17% of health care workers become sensitized. The recent
emphasis on universal precautions, with a concomitant marked increase in glove
usage, is largely blamed for the increase in allergy among health care workers.
Atopic individuals (those with other allergies or asthma) are at significantly
greater risk to develop latex allergy than the general population. It is
estimated that as many as 25-30% of atopic health care workers may become
sensitized. Another major issue is the cornstarch powder that has long been used in latex
gloves. Researchers have shown in several papers3,4 that cornstarch
powder binds the latex protein in the surgical glove, which allows the antigen
to reach both the wearer’s skin more easily (when the hand becomes moist during
surgery) and the patient’s skin. Also, when the surgeon both dons and removes
the glove, cornstarch powder is released into the air, and this becomes a
significant source of aerosolized latex protein that can sensitize health care
workers via inhalation. In a separate study done at the Mayo
Clinic,19 latex aeroallergen concentrations varied from 10 to 208
ng/m3 in areas where powdered latex gloves were used compared to 0.3
to 1.8 ng/m3 in areas where powdered latex gloves were never or
seldom used. Donald Beezhold has also written that body sweat inside latex
gloves may make latex proteins soluble, allowing absorption through skin and
sensitizing the wearer.4 He has reported that the amount of free
latex protein that can be extracted from powdered latex gloves is consistently
higher than the amount that is liberated from non-powdered gloves.
4,12 He has suggested that cornstarch powdered latex gloves should be
eliminated.2 Here is another thing to remember: not all latex gloves are created equal.
There are significant (sometimes astounding) differences between manufacturers
and product lines in the amount of free latex protein that can be liberated from
the glove and the number and types of chemicals used in glove production. Also,
gloves can be soaked after production to try to leach out the protein and
chemicals, and once more there will be differences between manufacturers in how
effectively these are removed. There is literature that clearly shows that some
brands of gloves are more allergenic than others.21 How are gloves made? Now on to some material about rubber in general and how gloves are
made.1,14,15,20 This will be brief - a more detailed review at a
level that a physician or nurse can understand is the article by Truscott.
20 In order to make a surgical glove, in addition to latex, one needs
water, vulcanizing agents, accelerators, activators, blockers, retarders,
anti-oxidants, preservatives, odorants, colorants, stabilizers, and processing
aids. In other words, you need a veritable chemical soup.CONTENTS
Selecting The
Right Glove: Understanding Latex Allergy And Glove Chemistry
What glove characteristics
should we look for?
Latex Allergy
How are gloves made?
Synthetic Rubbers
Synthetic Alternative
Gloves
Conclusions
References
Selecting The Right Glove: Understanding Latex Allergy And Glove
Chemistry
Picture courtesy Madegom Ltda. |
Latex is a natural product. Rubber trees (Hevea brasiliensis) produce the milky, viscous liquid. The tree bark can be shaved so that the latex bleeds, and it is then collected. Unless treated with chemicals soon after collection, the latex tends to harden into a gum. It was named rubber by the British chemist Joseph Priestly, who noticed that it could be used to rub away pencil marks. |
Natural latex is a polymer - that is, it is a long molecule composed of many repeating smaller molecular units. The basic unit of the polymer is called isoprene (synthetic rubbers use different chemicals as the basis for creating the polymer). Charles Goodyear first discovered a process that made rubber commercially useful. The story is that he accidentally dropped a mixture of rubber and sulfur into a fire. This produced a material that was no longer sticky, and had many desirable physical characteristics. Goodyear named this process vulcanization, after Vulcan, the Roman god of fire and craftwork. Vulcanized rubber is stronger yet also more elastic than the starting material. The sulfur cross-links the polymer chains in the latex. You can stretch vulcanized latex, but the polymer chains then snap back so the product returns to its original shape.
Nowadays, latex gloves are not produced with sulfur and fire. But sulfur is still very important as the primary vulcanizing agent. Accelerators are chemicals that speed the cross-linking process, either by donating sulfur atoms or because they are soluble within the natural rubber and help to draw the sulfur into the rubber by binding with sulfur. The major accelerators (and these are very important because they all can cause type IV allergy) are: thiurams, mercaptobenzothaizoles (usually abbreviated MBTs), and carbamates.
A second group of chemical sensitizers is the anti-oxidants. These are added to decrease the rate of rubber degradation. A wide variety of chemicals are available - glove manufacturers primarily use substituted phenols.
It is important to realize that different gloves will have different chemicals in differing concentrations in the final product. Also, since latex is a natural product, there will be some variation in the protein content from one lot to the next.
One brief comment about the word hypoallergenic - ignore it. The FDA proposed regulations in the summer of 1996 (which are not yet finalized as of this writing) that manufacturers not be permitted to use this term, since there is no established safe level below which latex protein or glove chemicals might not be harmful.
Gloves are created by dipping forms (which look like hands) into vats of liquid latex and admixed chemicals. The latex glove then hardens on the mold - it is formed with what will ultimately be the inside of the glove (touching your skin) on the outside of the mold. Then the gloves, still on the mold, go through one or more rinses to leach out protein and residual chemical (better rinsing equals less residua). Finally, the finished product is stripped off the mold, packaged, and sterilized.
What about synthetic rubbers? Remember that most of the world’s natural rubber trees are found in tropical countries such as Malaysia. During World War II, the supply of natural rubber from the Far East was disrupted. This led to the development of synthetic rubbers. Various types of synthetic rubber are in production around the world today - the properties of the end product depend on the chemical that is used as the building block to form the final polymer. Much of the world’s synthetic rubber is made from styrene and butadiene, which are found in petroleum. For our purposes, here is a list of synthetic rubbers used in making non-latex surgical gloves and some of the brand names: |
Synthetic Rubber | Glove name | Manufacturer |
---|---|---|
Polychloroprene (Neoprene) | Duraprene | Baxter |
Dermaprene | Ansell | |
Biogel Neo-tech | Regent | |
Neolon | Maxxim | |
Styrene butadiene | Elastyren | Hermal |
Styrene ethylene butadiene | Allergard | J and J |
Tactyl 1 | SmartPractice | |
Synthesys | SmartPractice |
Even with synthetic rubbers, there are still numerous chemicals (carbamates, etc.) involved in manufacture. Once more, there will be differences from one manufacturer to the next. It is still possible to have a serious type IV allergic reaction (contact dermatitis) to a synthetic rubber. However, type I natural latex allergy does not occur in response to synthetic rubber and these gloves are therefore required when treating a patient with known type I hypersensitivity, or for the health care worker who has either become type I sensitized or cannot find a suitable latex glove because of type IV allergy.
Conclusions
Clearly, we need gloves that provide excellent barrier protection, surgeon comfort, and acceptable cost. I would add that the literature indicates that the ideal glove, if it is latex, should be powder free, very low in extractable latex protein, and have the smallest concentration and the fewest number of residual chemicals from manufacture 6,18 Even when considering glove selection from the cost side alone, the cost at the time of purchase is only one part of the equation. As Fay7 points out, failed (torn) gloves cost the hospital money for replacement and waste removal, and one needs to consider the very real costs of providing the more expensive synthetic gloves for workers who become sensitized to latex or the major costs of disability payments for those who become so seriously sensitized that they are occupationally disabled.8,18 The risk of serious allergic reactions in patients who are already sensitized to latex must not be overlooked.
Alternately, the surgeon might consider that perhaps the ideal surgical glove is a synthetic rubber, such as polychloroprene (Neoprene) or one of the copolymers that contain styrene and butadiene. But there are pitfalls to this approach as well. The barrier properties of nonlatex synthetic rubber gloves are not as clearly defined. The cost of the synthetics is greater. The user still needs to pay attention to the chemical composition of the glove, because dangerous type IV reactions are possible. And the surgeon who chooses synthetic rubber gloves should be prepared to potentially sacrifice on glove comfort, dexterity, and grip because the fit, feel, and elasticity of the synthetic materials differ from natural rubber latex.
Glove choice should also be appropriate to the situation. One should consider wearing non-latex gloves (such as vinyl) when the superior barrier protection of latex is not needed. So, for example, a very short (less than 10-15 minute) procedure with minimal prospect for blood or body fluid contact might be one for which a vinyl glove could be considered an acceptable choice. Non-latex gloves may also be appropriate for the nurse who preps the surgical site prior to the start of surgery if the patient’s skin is intact, making body fluid contact highly unlikely.
In addition, here are a few common sense reminders.13 Prior to use, medical gloves should not be stored under conditions of excess heat or light, nor be near sources of ionizing radiation, since this will cause more rapid rubber degradation. Health care workers should be sure to remove gloves promptly when completing a procedure, and then wash his or her hands after glove use to minimize skin contact time with potential allergens. Also, health care workers should avoid touching their eyes, noses, or mouths while wearing latex or immediately upon removing a latex glove, in order to avoid potential latex sensitization via these mucosal routes.
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