BACKGROUND: Fifty percent of Australians use complementary and alternative 
medicines (other than vitamins) in any 12-month period, of which 
echinacea-containing products are increasingly popular. Recent reports have 
highlighted the risk of allergic reactions to complementary medicines in atopic 
patients.
OBJECTIVE: To determine the characteristics of adverse reactions linked to use 
of the popular herbal remedy echinacea.
METHODS: Five privately referred patients were evaluated by the authors in their 
office practice via skin prick testing (SPT) on the volar aspect of the forearm 
and radioallergosorbent test after adverse reactions to echinacea. As there was 
little published information on adverse reactions to echinacea, reports to the 
Australian Adverse Drug Reactions Advisory Committee were reviewed. Those 
suggestive of possible allergic reactions were evaluated in greater detail by 
anonymously surveying the healthcare professionals who had reported the cases 
and from one unreported case. Serum was collected for further analysis where 
possible.
RESULTS: Five cases of adverse reactions to echinacea were personally evaluated 
by the authors. Two patients suffered anaphylaxis and a third had an acute 
asthma attack 10 minutes after their first ever dose of echinacea. The fourth 
patient suffered recurrent episodes of mild asthma each time echinacea was 
ingested, and the fifth developed a maculopapular rash within 2 days of 
ingestion which recurred when rechallenged. Three of the patients had positive 
SPT results. Three reported repeated spontaneous "challenges" and symptoms after 
further ingestion of echinacea. Fifty-one Australian adverse drug reports 
implicating echinacea were also reviewed. There were 26 cases suggestive of 
possible immunoglobulin E-mediated hypersensitivity (4 anaphylaxis, 12 acute 
asthma, 10 urticaria/angioedema). Of these 26 patients, age ranged from 2 to 58 
years, 78% were female and >50% were known to be atopic. Four were hospitalized, 
4 reacted after their first known exposure, and 1 patient suffered multiple 
progressive systemic reactions. Twenty percent of 100 atopic subjects who had 
never taken echinacea also had positive SPT results to this substance when 
tested by one of the authors in his office practice.
CONCLUSION: Some atopic subjects have positive SPT results to echinacea in the 
absence of known exposure. Atopic subjects are also overrepresented in those 
experiencing reactions to echinacea. The possibility that cross-reactivity 
between echinacea and other environmental allergens may trigger allergic 
reactions in "echinacea-naïve" subjects is supported by the Australian data. 
Given its widespread (and largely unsupervised) community use, even rare adverse 
events become inevitable. Atopic patients should be cautioned appropriately.