Understanding Latex Allergy
in the Healthcare Setting

GLOVE MANUFACTURING PROCESS The manufacturing of gloves is a complex process involving latex concentrates mixed with various compounding chemicals, antioxidants, and accelerants to produce the thin barrier protection required by healthcare professionals. Gloves are manufactured using machines that have proprietary features suited to their own manufacturing processes. The sequence is illustrated below for both powdered and powder-free gloves. See Diagram below. Formers, made of material that can withstand high temperatures (usually porcelain), are used to manufacture gloves. Formers must be clean so that the latex deposition can be even and continuous. The former is then coated with a coagulant, which assists in controlling the amount of latex that will be deposited on the glove, and also ensures that the rubber will not adhere to the former. The clean and newly coated former then passes into a latex solution. The solution may be an NRL or non-latex compound, depending on what gloves are scheduled for manufacture on the particular run. The latex is allowed to build up some wet-gel strength before an initial leaching. The leaching is effective in removing residual calcium nitrate and soluble proteins. Hot water is used and the tanks are continuously replenished with fresh water. It is here that the process deviates, depending on whether powder-free or powdered gloves are being manufactured. Powder-free glove manufacturing includes the application of an inner surface polymer (for ease of donning) and curing. Polymer coatings are classified as hydrogels and non-hydrogels. Hydrogel coatings are composed of materials that absorb water many times their weight and become swollen and slippery so that the glove may be donned. Non-hydrogel polymers such as acrylic polyurethane, silicon polymer, or polymer blends repel water and the surface coating mimics the characteristics of a powdered surface. Polymers are used as coatings on the inner surface of gloves for ease of donning, while chlorination is applied to the outer surface to improve the grip feature of the glove. Gloves that are double-chlorinated (leached) have a smoother feel and will not stick together (referred to as blocking) in the package. On-line leaching (washing), the use of the chlorination process, and high-temperature washing of gloves after they are removed from the formers are all highly effective methods to reduce watersoluble latex allergenic proteins from the final latex glove product (powder-free and powdered). ROLE OF CHEMICAL ACCELERATORS Compounding of the raw “field” latex or non-latex material to a final solution suitable for the manufacturer’s glove products is another proprietary process. Chemicals are used in this “recipe.” These chemicals accelerate the bonding process of the gloving material during the manufacturing process. Accelerator chemicals help to tighten the glove matrix, improve and enhance barrier performance, and stabilize the raw gloving material. Sulfur is used to assist bonding of the glove material to form a product with superior stretch and recoil. It also adds strength to the glove, gives integrity to the latex during use, and stabilizes the latex for long-term storage. Chemical accelerators are, for the most part, used up during curing and in the washing and leaching portions of the manufacturing process. Accelerator chemicals can cause Type IV allergies in those individuals at risk. The chemicals most often implicated in Type IV allergies are mercaptobenzothiazoles (MBTs), thiurams, and carbamates (dithiocarbamates). Thiurams are regarded as the most common cause of Type IV delayed contact dermatitis. Thiurams decompose during vulcanization, liberating the sulfur and carbamates (dithiocarbamates). MBTs are an important accelerator because of their solubility in natural rubber latex. Their use in glove production is less frequent, and so the incidence of sensitization is lower than for other accelerator compounds. Carbamates (dithiocarbamates) facilitate cross-linking and curing by absorbing sulfur and carrying it into the glove material. There are more than 34 types of dithiocarbamates, and they are even less sensitizing than thiurams and MBTs. These compounds contain zinc, which is important to the solubility of the accelerator in natural rubber latex and its ability to react with sulfur. DEVELOPMENTS IN NATURAL RUBBER LATEX MANUFACTURING Manufacturers are constantly working to produce latex products that contain less latex allergen. As these products become more readily available, the risk of reactions in people sensitive to latex, as well as the risk of more people developing latex allergy, should decrease. Improved test methodologies have been developed that allow manufacturers to easily conduct testing within their labs, and they have been able to investigate the various parts of their processes that will impact the reduction of water-soluble latex proteins. Various approaches have been employed to reduce these proteins; for example: High-temperature post-washing (described and diagrammed previously) On-line leaching and washing (described and diagrammed previously) Utilization of chlorination processes (described and diagrammed previously) The development of de-proteinized and purified (DPNR) NRL – entails treating the latex obtained in the field with proteolytic enzymes NRL gloves still remain the barrier of choice among healthcare professionals. Manufacturers have developed technologies that allow them to produce low-allergen as well as synthetic gloves. Due to the water-soluble nature of latex proteins, most are leached out in the washing phases of the manufacturing process. High-temperature washing is a proven technology and the most effective way to reduce the allergen content of NRL gloves.

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