Abstract
Guayule natural rubber is commercially available as an emulsion base-material for latex medical devices, including medical gloves and catheters. These products do not cause reactions in Type I latex allergic humans. In addition to natural rubber, guayule produces terpene resin comprised of hundreds of isoprenoid compounds. One group, the guayulins, is a major terpenoid component of guayule resin; the most abundant, guayulin A, comprises 1–10% of the resin fraction. An earlier study concluded that guayulins are contact sensitizers in guinea pigs, although they appeared much less sensitizing in humans. The possibility that residual guayulins may be present in the guayule natural rubber emulsions at a sensitizing level is of concern.
We quantified the levels of guayulin and resin in purified natural rubber emulsions, using HPLC. Guayulin concentrations fell rapidly, due to hydrolysis at high pH, reaching a steady state after 4–6 weeks. The localized lymph node assay (LLNA) in mice was used to assess sensitization potential of guayule resin and guayulin A. Guinea pig patch tests were used to assess irritation and sensitization. Mouse ear swelling and rabbit repeated patch testing were used to assess irritation.
No sensitization or irritation by guayulin A was observed. Guayule resin was irritating at concentrations of 10% and above, but no sensitization occurred. The LLNA and dermal test data indicate that it is extremely unlikely that guayule latex products will cause sensitization or irritation due to the presence of trace guayulins or other resin compounds co-extracted with the guayule natural rubber emulsion.