Last week, a friend had failed to show up at the pub emailed next day with an excuse. "This cold is sending me batty," he wrote. "I've consumed my own body weight in echinacea and lemons!" The comment was offered without explanation, as if everyone would know what echinacea was. Somehow, this native American snakebite remedy has become as commonplace as paracetamol. Millions of us reach for the brown dropper bottle as soon as the first signs of a cold appear, hoping to nip it in the bud. Diluted in water and taken three times a day, echinacea is the new Night Nurse.
Though the herb has sprung to household prominence only in the past five years, it has a long and distinguished history. For centuries, the Sioux and other tribes used it to treat venomous snake and insect bites, ulcers, sores and any disease (notably syphilis) involving foul-smelling discharges or putrefying flesh.
More recently, Echinacea angustifolia - a wildflower native to North America and related to the daisy - was studied in depth by the Eclectics, a group of American medical herbalists practising from the 1850s to the 1930s. After observing its effects in hospitals for 80 years, they concluded that echinacea did indeed fight infection and treat conditions such as gangrene, bronchitis, tuberculosis, typhoid, meningitis and smallpox. Writing in 1922, however, the Eclectic physician Harvey Wickes Felter admitted there was "no satisfactory explanation" of how it worked.
Since then, more than 350 research projects have addressed precisely that question. Some have looked at how echinacea increases the activity of white blood cells (the "T cells" that fight infection), others at how it boosts production of interferon - a substance known to combat viruses. One discovery has been that echinacea also inhibits hyalurinadase, an enzyme that breaks down cell walls and forms pus - just as the Native Americans suspected.
Impressive though this body of evidence is, it is considerably flawed. To begin with, the researchers have been investigating the wrong plant. Most studies have used E. purpurea rather than E. angustifolia, which isn't the same thing at all. Though E. purpurea has similar medicinal qualities and is better researched scientifically, purists prefer the variety chronicled for centuries. However, E. purpurea is cheap, easily cultivated in Europe and available from most garden centres. This has enabled manufacturers to keep their prices down.
What's more, though evidence of echinacea's efficacy is convincing, most trials have been conducted on animals, not humans. "More science needs to be applied and people have to put aside their prejudices," says Michael McIntyre, president of the European Herbal Practitioners Association. "They shouldn't use a particular type of herb just because it is widely available. E. purpurea does work, but further research is needed. Right now, echinacea's popularity is due to word of mouth, not credible science. That's why it's so big."
Unfortunately, the same lack of rigour is apparent in accounts of echinacea's side effects. The Commission E Monograph, a German document regarded as the holy grail of herbalism by orthodox doctors, makes all kinds of pronouncements about the herb's "contraindications" - the circumstances in which it should not be prescribed. These recommendations have been misinterpreted in a game of Chinese whispers.
Though most herbalists agree that neither variety should be taken while pregnant or breastfeeding (due to lack of data), some are perplexed that echinacea is deemed unsuitable for asthmatics, diabetics and anyone with an auto-immune disease such as multiple sclerosis. "I have yet to see the research that underpins that," says McIntyre, "and I think it comes from a misunderstanding of how echinacea works. It is based on the theoretical risk that it may lead to an overactive immune system and change the body's metabolism. In fact, echinacea doesn't stimulate the immune system but normalises it."
Perversely, though it is sometimes used to treat hayfever, echinacea can cause severe reactions in those allergic to daisies. It is also known to produce a tickling sore throat when used in excess. It is unwise to take echinacea for more than eight weeks without a break - and tell your doctor you are taking it. Like many herbal extracts, this one reacts badly with some drugs, such as anabolic steroids.
· Next time: St John's wort
