The naturally occurring proteins are present either as water soluble (and therefore extractable) protein, or as "bound" protein - protein which is bound to the rubber molecules. Amongst these proteins are the enzymes involved in the biosynthesis of the rubber itself.
Some proteins are useful in latex manufacturing. In particular, those proteins associated with the rubber are important in maintaining the colloidal stability of the latex, but those found in the aqueous phase (also called the "serum") are thought to have "little technological significance" Citation:Pendle 1992 Maryland Conference sensitivity latex
Those proteins associated with the rubber molecules are insoluble, and
therefore non-extractable.
They cannot usually be leached from the latex while it
is being worn, and thus are
unable to cause an allergic reaction.
Footnote: It is possible to inadvertently
increase the amount of extractable protein by the addition of
detergents or
potassium hydroxide which disassociates the protein from the rubber
molecules.
Citation:hamann kick cutis 1993
Because some protein is "extractable" by aqueous methods, it has generally been accepted that moisture on the skin (sweat) can extract the protein from the glove and onto the wearers skin, where it can cause a Type I allergic reaction in sensitised individuals (see ______ by ____ elsewhere in this supplement). The rapid reaction of a patient to direct tissue contact with a latex glove suggests that the proteins are released upon contact, and that neither sweating of the hand nor prolonged exposure is necessary to liberate the proteins from surgical gloves. Citation:Fay Regent Issues latex safety medical environment
The route of exposure is particularly important in determining the extent of the reaction. For example Citation:Sussman Allergy Proc 1992 latex allergy importance clinical practice
Cutaneous exposure can cause itching, eczema and dermatitis,
Airborne exposure can cause rhinitis, conjunctivitis and asthma,
Mucosal and parenteral exposure may lead to anaphylaxis.
In the USA a number of cases have been recorded of death from anaphylaxis during barium enema procedures due to Type I reactions to the latex cuff on the rectal catheter.
Other latex medical and non-medical products may cause sensitisation to latex proteins, including
Condoms
Urinary catheters
Rubber dental dams
Kitchen gloves
Rubber toy balloons
It is worthwhile noting that products made from dry rubber (that is, the latex is coagulated, "crumbled", washed and dried) have extremely low levels of extractable protein Citation:Yip Turjanmaa Ng Mok J. nat Rubb Res 1994 allergic responses extractable proteins and very low or negligible allergenicity, probably due to the high temperatures achieved during the moulding process.
Pete Phillips <pete@smtl.co.uk>