An investigation on in vivo allergenicity of Artemisia annua leaves and stems.

Pollen of Artemisia annua is considered to be one of the most important allergens in autumnal hay fever in China, just as ragweed is in North America. In order to clarify the allergenicity of non-pollen containing components of the plant, Artemisia annua leaves and stems were collected and extracted before pollination time. The extracts of these pollen-free plant components were studied for allergenic activities using skin prick tests, intradermal tests, intranasal challenge and bronchial provocation tests. In 52 subjects sensitive to Artemisia pollen, 92.3% gave positive responses in skin prick tests, 100% gave positive responses in intradermal tests, 66.7% gave positive responses in intranasal challenge and 59.3% gave positive responses in bronchial provocation tests. Negative results to skin prick tests, intradermal tests and bronchial provocation tests were revealed in 30 seasonal asthmatics who gave negative responses to the pollen skin tests. Strict placebo control showed all negative tests in non-atopic adult human volunteers. We concluded that pollen-free plant extracts did have in vivo allergenic activities. Analysis of the plant allergenic components in vitro will be the subject of further studies.