Abstract

It is argued that latex protein allergy is in many respect a quasi-political problem with considerable similarities to those associated with exports of hormone-treated beef and genetically-modified cereals to Europe from the USA. In the case of the exports "US experts" argue that the materials are "safe", whereas similar "US experts" argue that latex products are "harmful" and restrictions should be placed on their use.

Many of those who claim to be allergic to latex protein are also allergic to a wide range of other common substances, notably peanuts and various cereal products. Great care has been taken by the American agencies not to implicate corn starch (which could be home grown), although it clearly is a vital issue in the low humidity environments of American hospitals. The very home-grown peanut, a significant cause of infant mortality, is treated on a very different plane from the imported latex gloves.

Natural rubber latex products had been marketed on a relatively large scale for sixty years between the 1930s. and the late 1980s without any serious suspicion of health risk to the users. Products included baby bottle teats, elastic thread, gloves, condoms and foam rubber. Furthermore, some of these items had been used by infants without any apparent danger through several generations. Further evidence of the benign nature of natural rubber latex as such is that lightly compounded latex concentrate has been used as an adhesive with children for many years, but it is probable (and fortunate) that the public is unaware of this use.

Allergic reactions to rubber products, made from both natural and a wide variety of synthetic rubbers, have been known for many years¹. The vast majority of these reactions (usually known as Type IV allergies) can be traced to the residues from accelerators and other compounding ingredients. In products expected to come into contact with human skin these materials are either avoided, or alternatives, based on other chemicals, are provided for those who are liable to become sensitized. It needs to be emphasized that such reactions are also liable to be experienced with most synthetic elastomers, and in some cases these may be more severe, as users of nitrile gloves are now reporting on the Internet.

Until as recently as 1989, it was rare to suspect that people could be allergic to natural rubber as such. Indeed there has been a long history of using rubber in relatively close proximity with the human body in products like gloves, hot water bottles, adhesive plasters, garment thread and so on without anyone experiencing any form of allergic reaction apart from those traceable to compounding ingredients, especially accelerator residues. In many cases rubber products were, and continue to be, used in products to avoid health problems associated with other materials. Thus foam rubber mattresses and pillows are considered to be more hygienic than similar soft furnishings filled with textiles.

Thus the "latex protein allergy problem" appears to be a relatively recent phenomenon although some medical researchers have attempted to show that there is a "long history" of allergic response to proteins. There is absolutely no reference to allergy, or health problems in any of the early textbooks on latex, although several of them are extremely thorough. Nevertheless, there was a flurry of activity on the Internet when a paper² on allergic reactions to electricians' gloves dating back to 1933 was found. The reactions were clearly due either to the accelerators used, or to an excessive residual quantity of these. There was no accompanying comment to note that the alpha-naphthylamine noted as being "slightly toxic" in this reference was subsequently found to be highly carcinogenic!

The problem stems from the vastly increased use of medical gloves which emerged once it was realised that these could form a vital barrier against the transmission of HIV (the AIDS virus) and hepatitis. This response was greatest in the USA, where the dread of catching AIDS was extreme and led the Government to stipulate the so-called "universal precautions" to inhibit this transmission. These measures include the use of disposable medical gloves wherever there is a risk of contact with a wide range of bodily excretions including blood. The increase in demand (the USA imported 20 billion medical gloves in 1996 as compared with 6 billion in 1991) was sufficient to lead to a short-term rise in the price of natural rubber, and as will be noted an equally sharp and short-term decline in manufacturing standards.

There was a certain inevitability that once universal barrier precautions were adopted that some (where some is difficult to measure with any degree of accuracy) might become sensitive to latex films, or more properly, to the accelerators used to cure them, or to the residual proteins within such films. Furthermore, as the original mandate had come from a Government agency then it was similarly inevitable that this agency, or another one, would introduce measures aimed at limiting this new "risk".

References
¹Nutt, A.R. Toxic hazards of rubber chemicals. London: Elsevier, 1984.
²Downing, J.G. Dermatitis from rubber gloves. New England Journal of Medicine, 1933, 208, 196.