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Natural rubber latex is known to trigger allergic reactions in certain individuals. Given this, recent studies and innovations are coming up with allergy-free alternatives, says Angelica Buan in this article.
Got an itch? Chances are you must be sensitive to products that may contain allergenic substances, including latex.
Natural rubber (NR) latex allergies can range from mild symptoms such as hives to life-threatening, such as anaphylactic shock. Although rubber gloves have earned the brunt of causing allergies to wearers, NR latex is used in more common products – from rubber bands and balloons to mattresses and sexual wellness products.
Latex products are made from a milky fluid obtained from the rubber tree, Hevea brasiliensis. According to The National Institute for Occupational Safety and Health (NIOSH), some chemicals are also added to the sap during the processing and manufacture of commercial latex. Certain proteins in latex trigger the allergic reactions in individuals sensitive to this.
The prevalence of Type 1 allergies or those caused by latex is relatively small by global estimates, representing 1-6% of the overall population.
Health care workers and frequent users of latex gloves are at highest risk of developing allergies, according to the Occupational Safety and Health Administration (OSHA). It estimates that 8-12% of health care workers are latex-sensitive, while workers in factories that produce NR latex or products with NR latex might also be at risk.
The Australasian Society of Clinical Immunology and Allergy suggests the use of non-powdered latex gloves, particularly in health care settings.
Differentiating the triggering products
While there is currently no available standard testing to provide consistent identification of allergy-causing proteins (antigens) and their concentrations, according to NIOSH, total protein serves as a useful indicator of the exposure.
According to the American Latex Allergy Association (ALAA), concern for allergy to NR latex proteins, while heightened by the late 1980s, has seen new cases of latex allergy decreasing. Nonetheless our exposure to latex-containing products does not abate the risk to developing allergies at any time.
Latex-free labelling initially ushered the solution to determining which products could trigger allergies. Later on, it was found to provide inaccurate information.
For this reason, the US-based Food and Drug Administration (FDA) cautioned against mislabelling products as “latex-free”. The advisory called, “Don’t be Misled by Latex Free Claims” supplements a guidance document it issued in December 2014 in the Federal Register, recommending manufacturers of gloves, condoms, catheters and other medical devices to refrain from using labels with “latex-free” or “does not contain latex” claims.
It said in its recent advisory that since there are no existing tests yet that can prove a product has no NR latex proteins (that can cause allergic reactions), thus, such a claim is “scientifically inaccurate and misleading”. Moreover, the latex-free labels on products such as PVC and nitrile gloves, which contain synthetic latex and do not trigger latex allergy, can be “confusing”, it added.
Meanwhile, manufacturers and suppliers of latex products expressed mixed reactions over this directive. While others are agreeable to the recommendation, others are still reviewing the advisory to be able to make necessary adjustments.
Latex-free innovations
To date, the development of products that are NR latex-free are already underway, while several are either already in the market or awaiting commercial production.
For instance, scientists at the College of Food, Agricultural, and Environmental Sciences (CFAES) of the Ohio State University have developed a latex film made from guayule, a desert shrub native to South West US & Mexico that is known to be an alternative source for rubber and is safe for NR latex-sensitive individuals. Guayule latex is naturally Type I-hypoallergenic.
Led by university scholar, Katrina Cornish, the research team has made guayule and Hevea gloves Type IV-hypoallergenic, by using new accelerators, chemicals added to expedite the curing reactions and production of latex products and that don’t leave allergy-causing residues in the finished product.
US-headquartered start-up company EnergyEne Inc has been established to lead the development and commercialisation of products from the patentpending latex thin films, said to possess mechanical properties suitable for surgical gloves, catheters and condoms.
Meanwhile, a new latex-replacement substance called hydrogel is being utilised by Australian scientists to develop condoms. Unlike latex, the hydrogel enables the condom material to feel like skin. Hydrogels are already being widely used in prosthetics, having properties close to tissue.
According to the researchers from the University of Wollongong (UOW), among the unique advantages of hydrogels are that it can be engineered to perform all kinds of different functionalities, such as self-lubrication, topical drug delivery, biodegradability and even electric conductivity.
The team received a grant from the Bill and Melinda Gates Foundation, which called for the development of next generation condoms.
The study will also conduct a biometric testing to determine response as to whether the hydrogel-based condom is better than the latex one.
Harvesting non-allergenic sources
The increasing incidences of allergic reactions to proteins in NR latex spurred the need to develop alternative rubber sources.
While over 2,000 different plant species are known to produce rubber, only a few of the plant species are capable of producing large amounts of high quality rubber, according to the University of Nevada in the US.
At least four plant sources are currently in the headlines and being eyed for high quality rubber, without the risk of causing allergic responses.
One of these is the prickly lettuce, identified by scientists at the Washington State University. The team identified regions in the genetic code of this common plant that is tied to rubber production.
Although needing further study, the scientists claim that the prickly lettuce could be cultivated for latex production. The multiple stems of the plant will also allow for maximum rubber yield. It can also be grown with minimal rainfall and as cash crop in rotation with other crops.
Researchers at the German Münster University, a branch of the Fraunhofer Institute for Molecular Biology and Applied Ecology IME, the Technische Universität München (TUM) and TRM in York, UK, have recently identified the protein in the Russian dandelion, the so-called rubber transferase activator that plays a key role in forming the rubber producing complex in the flower. A second study identified a further important protein, which is vital in the formation of the long polyisoprene chains. These polymers give the rubber its elasticity and resilience.
Their recent findings on the dandelions have brought closer the possibility of finally manufacturing natural rubber biotechnologically. The German Federal Environmental Foundation (DBU), and the German Federal Ministry of Food and Agriculture, supported the research.
In view of this development, a report on the natural rubber producing plants published in 2013 in the African Journal of Biotechnology indicated the potential of the dandelion rubber in a host of applications, primarily in tyres. It projected that the industry will see its first dandelion rubber facility within the decade. By 2020, more than 27 million kg of natural rubber could be produced from dandelions.
Meanwhile, guayule has already outpaced the other alternative rubber sources in terms of R&D on its potential for commercial-scale production, being endowed with latex that has similar properties to that of the natural rubber.
Mostly venturing on developing guayule are tyre makers. Bridgestone Americas has built a 4-ha Biorubber Research Centre in Arizona, and started production of guayule rubber in 2014, expecting to produce fully sustainable and renewable raw materials from guayule by 2050.
Cooper Tire & Rubber has also dug into developing the shrub’s potentials, with a US$6.9 million grant from the US Department of Energy supporting its research. It is conducting ongoing tests on the guayule tyre build it completed last year.
On the other hand, Arizona-based bio-agriculture firm PanAridus, which partnered with Cooper in 2013 for the guayule biorubber consortium, has shipped its first bale of tyre-grade guayule rubber after it obtained a patent last year.
Other identified natural rubber alternative sources being eyed for further study are the sunflower, which incidentally is a distant relative of guayule; and the Gutta Percha – trees found in East Asia, mostly of the Palaquium genus, that has potential to produce rigid latex.