Primula obconica--is contact allergy on the decline?

Primula obconica, a member of the Primulaceae family, was introduced to Britain from China in 1880. P. obconica cultivars, which are reputed to contain less primin, have been developed over the past number of years in an attempt to reduce the incidence of allergic contact dermatitis. Primin (2-methoxy-6-pentyl-1,4-benzoquinone) is the main sensitizer, although other allergens have been postulated. We believe the incidence of primula allergic contact dermatitis has fallen since the introduction of primin-free P. obconica into the European market and thus the aims of this study were twofold. First, to determine whether the incidence of primula allergic contact dermatitis was truly on the decline and, second, to confirm the presence of primin-free P. obconica in the UK. We surveyed the incidence of primula allergic contact dermatitis in the UK and compared the incidence in the period between 1995 and 2000 with a subsequent follow-up study looking at the incidence for 2002. The results showed a significant fall in primin-positive patch tests from 1995 to 2000. The follow-up results for 2002 showed a further reduction in the number of primin-positive patch tests. The yearly incidence of contact allergy to primin has fallen from 0.785% in 1995/1996 to 0.429% in 2002. This downward trend was statistically significant (P = 0.001). A telephone survey of UK seed suppliers and selected plant retailers was also undertaken to clarify what types of P. obconica were available for sale and to assess suppliers' and retailers' knowledge of the primin-free varieties. This survey showed that 50% of suppliers were selling primin-free varieties but that the majority of surveyed retailers were not currently selling any variety of P. obconica. Our study suggests that although the yearly incidence of contact allergy to primin has fallen significantly over the past 8 years, it is still an important allergen, and thus its inclusion in the standard series remains justified for the foreseeable future.