Echinacea: The genus Echinacea

234 Echinacea: The genus Echinacea
When interpreting reports of immediate hypersensitivity to Asteraceae-derived CAM, it is
helpful to bear in mind a number of important concepts: (1) exposure to Asteraceae is common;
(2) sensitization is more common in subjects with preexistent allergic disease; (3) there is allergenic
cross-reactivity between different Asteraceae, and between Asteraceae and some foods; and (4)
patients sensitized by inhalation may experience allergic reactions when exposed by other routes.
The implication is that unexpected adverse reactions may occur even with first ever known exposure.
Not all adverse reactions to Asteraceae, however, are IgE mediated. Some patients will experience
delayed hypersensitivity. Others experience adverse effects where the mechanism is poorly
defined. An important implication is that not all adverse reactions will be confined to atopics, but
may extend to others with undefined risk factors. Adverse reactions are summarized in Table 17.1.
IMMEDIATE HYPERSENSITIVITY REACTIONS
With over 20,000 species of Asteraceae distributed worldwide (absent only from the Antarctic
mainland (Jeffery, 1978), exposure to inhaled or ingested members of this family is inevitable.
Echinacea (or coneflower) is a flowering member of the Asteraceae (Compositae) family whose
other members include Ambrosia (ragweed) species, Artemisia (mugwort, sagebrush, wormwood)
species, Parthenium (feverfew), and cultivated plants including chrysanthemums, dahlias, sunflowers,
marigolds, safflower, and daisies (Platts-Mills and Solomon, 1993). Edible plants such as
lettuce, safflower, chicory, and artichoke are also Asteraceae. Some members are used as CAM,
including Echinacea, dandelion, chamomile, feverfew, milk thistle, and wormwood (Newall et al.,
1996).
Sensitization to Asteraceae is common. Asteraceae-derived pollens are an important trigger for
allergic rhinitis and asthma, including Ambrosia (ragweed) in North America, Parthenium (feverfew)
in South America and India, Artemisia (mugwort) in Spain, and Chrysanthemum and sunflower in
occupational and population settings (Atis et al., 2002; Bousquet et al., 1985; Goldberg et al., 1998;
Groenewoud et al., 2002; Jimenez et al., 1994; Kuroume et al., 1975; Negrini and Arobba, 1992;
Park et al., 1989; Sriramarao et al., 1991; Uter et al., 2001).
Cross-reactivity between inhaled and ingested allergen is a risk factor for allergic reactions
with exposure via other routes (reviewed in Baldo, 1996; Caballero and Martin-Esteban, 1998).
Precedents include oral allergy syndrome in pollen-sensitive subjects and some allergic reactions to
sunflower seeds and crustaceans (Axelsson et al., 1994; Caballero et al., 1994; Leung et al., 1996).
Sensitization to Asteraceae has also been associated with immediate hypersensitivity to CAM, such
as royal jelly, Echinacea, bee pollen extracts, and chamomile, and some foods such as celery, honey,
sunflower seeds, carrot, lettuce, watermelon, and nuts (Angiola Crivellaro et al., 2000; Axelsson et
al., 1994; Bauer et al., 1996; Bousquet et al., 1984; Cohen et al., 1979; Dawe et al., 1996; Dietschi
et al., 1987; Florido-Lopez et al., 1995; Garcia Ortiz et al., 1996; Helbling et al., 1992; Leung et al.,
1995; Lombardi et al., 1998; Reider et al., 2000; Subiza et al., 1989; Vallier et al., 1988; Vila et al.,
1998). An appreciation of the concept of cross-sensitization makes unexpected reactions to CAM
with first known exposure (such as to chamomile, Echinacea, royal jelly and pollen-derived products)
perhaps not so surprising after all (Lombardi et al., 1998, Mullins and Heddle, 2002; Subiza et al.,
1989).
These observations are consistent with the hypersensitivity reactions to Echinacea in Australian
subjects (Mullins and Heddle, 2002). Of 26 subjects with immediate hypersensitivity, 4 had anaphylaxis,
12 suffered acute asthma attacks, and 10 experienced urticaria/angioedema. Reactions were
not always mild: four were hospitalized, four reacted after their first ever known exposure, and one
patient suffered multiple progressive systemic allergic reactions. Echinacea was the sole implicated
medication in 15 cases.
Consistent with atopy being an important risk factor, over half were known to be atopic.
Furthermore, when 100 consecutive atopic patients were skin tested, 20 had positive reactions
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