BACKGROUND: The role of Melaleuca quinquenervia tree as a source of allergen(s) and respiratory irritant(s) is controversial. OBJECTIVE: Determine whether Melaleuca tree pollen or odor is medically important. METHODS: A 2-year aeroallergen survey and skin test (ST) results of 1,017 subjects were reviewed. Sixteen subjects were selected based on positive Melaleuca pollen extract (MPE) STs. Double-blind nasal challenges with MPE were performed on six subjects. Single-blind bronchial challenges with MPE were performed on four. To evaluate the irritant effect, 11 subjects received 34 different Melaleuca odor challenges (blossoms, bark, and leaves) through a closed system for up to 30 minutes. Four inhaled an odor from cajeput oil (derived from Melaleuca leaves) for 1 hour. Spirometry was performed before and after odor challenges. Radioallergosorbent test using MPE was compared with MPE STs in 15 subjects. RESULTS: The aeroallergens survey revealed insignificant numbers of Melaleuca pollen. Ninety-seven of 1,017 subjects were a 2+ or greater intradermal MPE ST. One of 6 double-blind nasal challenges and 1 of 4 single-blind bronchial challenges using MPE were positive in subjects with positive MPE STs. All 38 odor challenges with blossoms, bark, leaves, and cajeput oil were nonreactive. The MPE radioallergosorbent test correlated with MPE ST results. CONCLUSIONS: The Melaleuca tree is not a significant source of aeroallergen. The Melaleuca odor is not a respiratory irritant. MPE antigen(s) has been shown to cross-react with pollen extracts from a proven aeroallergen (Bahia grass pollen) possibly explaining the few cases of positive MPE STs with positive nasal/bronchial challenges.
BACKGROUND: The role of Melaleuca quinquenervia tree as a source of allergen(s) and respiratory irritant(s) is controversial. OBJECTIVE: Determine whether Melaleuca tree pollen or odor is medically important. METHODS: A 2-year aeroallergen survey and skin test (ST) results of 1,017 subjects were reviewed. Sixteen subjects were selected based on positive Melaleuca pollen extract (MPE) STs. Double-blind nasal challenges with MPE were performed on six subjects. Single-blind bronchial challenges with MPE were performed on four. To evaluate the irritant effect, 11 subjects received 34 different Melaleuca odor challenges (blossoms, bark, and leaves) through a closed system for up to 30 minutes. Four inhaled an odor from cajeput oil (derived from Melaleuca leaves) for 1 hour. Spirometry was performed before and after odor challenges. Radioallergosorbent test using MPE was compared with MPE STs in 15 subjects. RESULTS: The aeroallergens survey revealed insignificant numbers of Melaleuca pollen. Ninety-seven of 1,017 subjects were a 2+ or greater intradermal MPE ST. One of 6 double-blind nasal challenges and 1 of 4 single-blind bronchial challenges using MPE were positive in subjects with positive MPE STs. All 38 odor challenges with blossoms, bark, leaves, and cajeput oil were nonreactive. The MPE radioallergosorbent test correlated with MPE ST results. CONCLUSIONS: The Melaleuca tree is not a significant source of aeroallergen. The Melaleuca odor is not a respiratory irritant. MPE antigen(s) has been shown to cross-react with pollen extracts from a proven aeroallergen (Bahia grass pollen) possibly explaining the few cases of positive MPE STs with positive nasal/bronchial challenges.