Airborne contact dermatitis due to Japanese cedar pollen

Contact dermatitis caused by airborne antigen is a well-recognized problem. Previously, airborne contact dermatitis after contact with Japanese cedar pollen [Japanese cedar pollen dermatitis (JCPD)] has been reported in Japan. However, there is still no diagnostic test to evaluate contact dermatitis due to Japanese cedar pollen. Skin tests with Japanese cedar pollen have been used to investigate these patients. A histological analysis was also conducted to clarify the mechanism of JCPD. We performed a scratch-patch test, scratch test and assays for total immunoglobulin E (IgE) and specific IgE in 13 patients suspected to have skin symptoms from Japanese cedar pollen, 5 patients with Japanese cedar pollinosis and 15 control normal subjects. All subjects were tested with Japanese cedar pollen allergen extract. A skin biopsy was performed from a Japanese cedar pollen-scratch-patch-test positive in patients with JCPD. The result after 48 hr of scratch-patch test was compared with the patient's history and the findings of corresponding scratch test and specific IgE. 100% of the 13 patients with JCPD showed a positive scratch-patch-test reaction to Japanese cedar pollen extract. However, 20% of the patients with the Japanese cedar pollinosis without any eruptions showed a positive scratch-patch-test reaction. The percentage of positive results for specific IgE and the scratch test did not differ substantially between Japanese cedar pollionosis patients with a history of chronic erythema after contact with Japanese cedar pollen and those without such a history. No side-effects were observed regarding the scratch-patch test. Control subjects showed 7% positive reaction. Histological examination showed that eczematous change (spongiosis, intracellular oedema and acanthosis), and infiltration of lymphocytes and eosinophils were all observed at the scratch-patch-test-positive sites. We therefore concluded that the use of the scratch-patch test with Japanese cedar pollen extract was useful for accurately diagnosing JCPD.