Echinacea purp

Echinacea is the herb people buy in April for the winter ahead. These are the questions our naturopaths ask in store, and they're usually about which one rather than whether.

A good fit if

• Catching fewer colds is your goal, which is the only claim the combined evidence points towards
• You'll start before cold season rather than at the first sneeze, as the prevention trials ran for months
• You can find a product that names its species and plant part on the label
• You have no history of hay fever, asthma, eczema or other allergies
• You're an adult or a teenager over 12, which is where every regulator draws the line

Check with us first if

• You take any medicine that's processed by the liver. E. purpurea root sped up caffeine clearance by 34 per cent and changed CYP3A enzyme activity in opposite directions in the liver and gut, so its overall effect on a particular medicine can't be predicted.
• You have an autoimmune condition. Echinacea acts on the immune system, the research flags a caution, and there's a recorded case of pemphigus vulgaris (an autoimmune skin condition) getting worse.
• You're pregnant. One study following 206 exposed women, 112 in the first trimester, found no increase in major birth defects. That's reassuring, but it isn't an all-clear.
• You're breastfeeding. There's little data either way, so there's no basis for a recommendation.
• You have eyelid surgery coming up. It's best avoided because of the risk of dry eye.
• Your cold symptoms have already lasted more than 10 days, or they're getting worse rather than better.
• You take prescription medicines. Check with your doctor, pharmacist or our naturopaths before you start.

• E. purpurea fresh aerial parts, ethanolic extract. Best known for: The only echinacea material any major regulator grades as well-established use rather than traditional use. Absorption: Alkamides reach detectable plasma concentrations after oral dosing. Typical use: The prevention signal rests substantially on one manufacturer's 95 per cent herb, 5 per cent root fresh-plant extract. Including a 755-person, four-month placebo-controlled trial.
• E. purpurea pressed juice of fresh aerial parts. Best known for: Expressed juice rather than an alcohol extract, so lower in the fat-soluble alkamides. Absorption: Not established. Typical use: A 2,458-person meta-analysis found ethanolic extracts appeared to provide superior effects over pressed juices.
• E. purpurea root. Best known for: Root rather than aerial parts, rich in alkamides and characteristically carrying cichoric acid. Absorption: 1,600 mg a day produced measurable systemic pharmacological effect, so it is absorbed and active. Typical use: Graded traditional use only by the EMA, which notes insufficient evidence from clinical trials but calls effectiveness plausible.
• E. angustifolia root. Best known for: The species of the Native American and Eclectic tradition, and root only. Absorption: Three extraction methods were tested head to head. Supercritical CO2, 60 per cent ethanol and 20 per cent ethanol. Typical use: The cleanest negative trial in the family used this material: none of the three extracts affected rhinovirus infection or the illness that followed.
• E. pallida root. Best known for: Permitted in Australia and the least studied of the three species. Absorption: Not established. Typical use: No trial held here used it. There is no supported use to report, which is different from a use that failed.
• Liquid tonics and tinctures. Best known for: Alcohol extraction, closest in kind to the extracts that performed best, and flexible dosing. Absorption: Alkamides are absorbed orally. Typical use: The best-supported format, but only if the species and plant part underneath are the right ones.
• Capsules and tablets. Best known for: Usually dried root or extract powder, with dose per unit varying enormously between brands. Absorption: A trial delivering the equivalent of 10.2 g then 5.1 g of dried root a day confirmed systemic exposure and still found no efficacy. Typical use: Depends entirely on the material inside. The format tells you nothing.
• Tea. Best known for: Dried plant material infused in water. Absorption: Water extraction favours polysaccharides and caffeic acid derivatives; the fat-soluble alkamides are poorly extracted into water. Typical use: The weakest format evidence in the family. No trial held here used a tea.

Reference values. There isn't one, and there can't be. Echinacea is a herb, not a nutrient, so there's no recommended intake, no deficiency and no food sources. Any recommended daily intake idea simply doesn't apply.

Typical supplemental range. This is the weakest link, so it's worth saying plainly: there's no common unit across capsules, tonics and teas, so trial doses and shelf doses often can't be compared at all. The strongest treatment trial used the equivalent of 10.2 g of dried root in the first 24 hours, then 5.1 g a day for four days. A study of how it's absorbed used E. purpurea root at 400 mg four times a day. The two large prevention trials used a branded fresh-plant extract whose daily dose isn't given in the published summaries. Don't assume a product on the shelf matches a trial dose without checking its label against that trial.

Upper level. No daily cap on Australia's permitted ingredients list (Schedule 1) applies to any of the three species, and no upper limit has been set. That doesn't mean anything goes. A company still has to hold evidence for the dose it uses, and European guidance limits these medicines to adults and teenagers over 12, and to short courses.

Worth knowing. How long you take it matters more than the dose. European guidance is to get advice if cold symptoms last longer than 10 days or get worse, and for use on the skin beyond a week. The longest controlled prevention course we found ran for four months, with side effect rates similar to placebo (293 compared with 306). That's the best evidence available that a season-long course is well tolerated. What you need depends on your age, diet and health, so talk to one of our naturopaths.

This list is the part of the page we will not shorten. If any of it applies to you, talk to one of our naturopaths or your doctor before starting.

• Allergy to plants in the Asteraceae family. Ragweed, chrysanthemum, marigold, daisy. Absolute contraindication.
• Atopy. Hay fever, asthma, eczema or existing allergies. Anaphylaxis is documented in Australia; 19 per cent of surveyed atopic patients showed echinacea-binding IgE.
• Immunosuppressant medicines. Echinacea may antagonise their effect.
• Chemotherapy, and etoposide in particular. May reduce anticancer medication efficacy; thrombocytopenia case report.
• Autoimmune conditions. An immunomodulating herb in a condition of immune over-activity; exacerbation case reported.
• Medicines metabolised by CYP1A2 or CYP3A. Caffeine clearance rose 34 per cent and CYP3A activity shifted in opposite directions at two sites.
• Children under 12. No efficacy benefit, significantly more rash, and the European monograph excludes them.
• Pregnancy. One prospective cohort found no increase in major malformations; that is not a safety assurance.
• Breastfeeding. Little data exists either way.
• Eyelid surgery. Avoidance advised because of dry eye syndrome risk.
• Cold symptoms lasting more than 10 days, or worsening. Seek advice rather than continuing.
• Rare case reports include dermatitis, anaphylaxis, thrombotic thrombocytopenic purpura, leukopenia, acute hepatitis and acute liver failure in a 2-year-old; causation isn't established, but these are why the age and duration limits are real.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before starting.