The powder used in the manufacture of latex gloves provides several important functions. Principle among these is to prevent the freshly polymerized rubber, which is very tacky, from adhering to itself following its stripping from its mold. It also acts as a lubricant to facilitate glove donning. Talc, which is an inert silicate, was originally used for these purposes until it was discovered that it could cause granulomas when left in contact with exposed tissues during surgical procedures. For this reason, in the mid-seventies, the FDA banned the use of talc in surgical gloves. As a substitute, highly cross-linked dextran particles were utilized. The original reason for cross-linking the dextran was to make gloves autoclavable, plus it facilitated donning and did not swell when wet. By the mid-eighties, most manufacturers switched to cross-linked dextran powders for latex products manufactured via dipping molds.
The mid to late eighties is the approximate time when health related problems with latex gloves began to accelerate. It thus seemed natural to ask the question, was the change from talc to cross-linked dextran powder somehow involved in this increase? It should be noted that this is also the time when latex glove usage was rapidly increasing for protection against infectious diseases such as AIDS and hepatitis.
As more information on the etiology of these latex health related problems became available, it became apparent that sensitization to a number of the chemicals used to polymerize the latex were involved in causing contact dermatitis. It also was revealed that several of the proteins derived from the natural rubber latex were involved as allergens in inducing the Type I allergic immediate
hypersensitivity reactions. Since many of these symptoms were characteristic of airborne allergies, researchers began to speculate that the powder, which can become aerosolized with glove usage, carried these allergens. This would result in the possible dispersion of inhalable particles which could carry allergens to the respiratory tract resulting in subsequent sensitization and induction of symptoms via this route.
Several studies germane to this hypothesis have been published. One, at Johns Hopkins, demonstrated that proteins can bind to the cross-linked dextran; however, this was a very small percentage of the total extractable protein and the complexed protein bound only a small amount of latex specific IgE.1 Another study performed by Beezhold indicated that most of the proteins were associated with the powder.2 For lack of details these studies are difficult to interpret but could be alternatively explained by the possibility that their preparations were contaminated with proteins which copurified with the powder and were in fact not attached to it.
Our own experiments indicate that proteins elute from powdered gloves with different kinetics than the powder. Furthermore, while measuring the size of the protein associated particles resulting from snapping gloves, it became apparent that the protein is released in a much smaller particle size than the powder. Collectively, these findings indicate that the cross-linked dextran and protein are physically separated.
The role of the powder with respect to inducing Type I allergic disease is difficult to understand. For example, most of the powder grains are much too large (20-70 uM) to be inhaled and thus would not be expected to travel far into the respiratory tract. Furthermore, it is difficult to understand how the few allergens which were shown to be firmly attached to these particles could reach tissue mast cells as most would be trapped in the mucous lining and expelled accordingly. One might also be suspicious that even if the postulated protein coated powder did reach tissue mast cells how does one envisage these fixed proteins being able to cross-link the IgE on the surface of mast cells, a prerequisite for mediator release.
The cross-linked dextran is usually applied by dipping the latex gloves through a slurry containing wash fluid and cross-linked dextran. These particles, along with other eluted materials contained in the slurry, passively absorb to the latex. These other materials include proteins and possible bacterial products the concentration of which depend upon the size of the lot and how often the slurry baths are changed.3 The gloves which are treated in this way contain more protein and bacterial products than those produced in other ways. Furthermore, the bulk of these substances would be confined to the interior of the glove as they are inverted while being stripped from their molds. The association of higher protein levels in gloves dipped in such slurries may be the reason why the powder has been associated with problems from latex as most powdered gloves seem to be higher in proteins.
Studies indicate that the cross-linked dextran particles are quite dense and would be expected to settle rapidly from the air. This and other experiments which indicate that the powder and allergens are physically separated would indicate that the powder is not a carrier of latex allergens. On the other hand, it should be realized that the powder itself may be irritating to mucosal surfaces and cause a variety of nonspecific symptoms in susceptible individuals.
Present information makes it unlikely that the powder itself is contributing directly to the problems with latex gloves but does indicate that the methods of applying the powder may need to be altered. Therefore, until further studies are performed, it would be prudent to modify the method of applying the powder but premature to consider banning its use.
REFERENCES
- Tomazic VJ, Shampaine EL, Lamanna A, et al. Cornstarch powder on latex products is an allergen carrier. J. Allergy Clin Immunol 1994;93:751-8.
- Beezhold D, Beck WC. Surgical glove powders bind latex antigens. Arch Surg 1992;127:1354-7.
- Williams PB, Halsey JF. Endotoxin as a factor in adverse reactions to latex gloves. Accepted: Annals of Allergy Asthma Clin Immunol 1997.
