Respiratory tract reactions to western red cedar.

1 Asthma due to western red cedar (Thuja plicata) is well recognized, but has not been described frequently in the UK. Two patients who developed asthma and rhinitis due to occupational contact with western red cedar were studied. Both patients developed late asthmatic responses following bronchial challenge with western red cedar. 2 The challenge technique and the results of comparison between different wood dusts and dust extract are described. 3 The technique of anterior rhinometry was used to follow the nasal response to challenge in one patient, and demonstrated a late nasal reaction which followed a similar time course to the bronchial response.