Natural remedies for immunity
Direct answer
No supplement here has been shown to prevent infections or boost a healthy immune system. Vitamin C is rated Limited (2) for preventing colds, and echinacea and elderberry are also Limited (2). The caution that matters most is echinacea's risk of allergic reaction, which can be severe in people with daisy-family allergies, hay fever, asthma or eczema.
In general-community trials vitamin C made no meaningful difference to colds (risk ratio 0.97), though it about halved colds in marathon runners, skiers and soldiers under heavy physical stress (0.48). Quercetin is only Traditional (1) for immune protection in athletes.
Vitamin C above 1 g a day brings diarrhoea and, in men, more kidney stones.
Compare the options
Of the 4 remedies for immunity we have rated, none has better than Limited evidence. See our evidence report.
Click a column heading to sort.
| Rated for | Typical form & use | Main caution | |||
|---|---|---|---|---|---|
| Echinacea Echinacea purpurea/angustifolia | Limited | Preventing colds | E. purpurea juice, 6–9 ml a day | Allergy risk, esp. with daisy-family allergy | About a week |
| Elderberry Sambucus nigra (ripe fruit, cooked) | Limited | Preventing colds | Capsule extract, 300 mg 2–3 times a day | Raw or unripe berries, leaves and stems are toxic | 2–3 days |
| Vitamin C Ascorbic acid (water-soluble vitamin) | Limited | Preventing colds, oral | Tablet or capsule, 200 mg–1 g a day | Over 1 g/day: diarrhoea, and more stones in men | 4+ weeks |
| Quercetin Plant flavonoid (isolated compound) | Traditional | Immune protection in athletes | Capsule, about 1,000 mg daily | Can change how some medicines are absorbed | 4+ weeks |
- Rated for
- Preventing colds
- Form
- E. purpurea juice, 6–9 ml a day
- Onset
- About a week
- Rated for
- Preventing colds
- Form
- Capsule extract, 300 mg 2–3 times a day
- Onset
- 2–3 days
- Rated for
- Preventing colds, oral
- Form
- Tablet or capsule, 200 mg–1 g a day
- Onset
- 4+ weeks
- Rated for
- Immune protection in athletes
- Form
- Capsule, about 1,000 mg daily
- Onset
- 4+ weeks
Quick picks
Rated Limited (2) for preventing colds: the 2014 Cochrane review found no significant effect in any of its 12 prevention comparisons, though pooling them after the fact hinted at a 10% to 20% fewer colds. Two later meta-analyses report bigger effects for recurrent infections, but some authors of the 2024 one declare payments from an echinacea maker.
Gentlest optionElderberryRated Limited (2) for preventing colds: in the one air-travel trial 12 of 154 people on elderberry and 17 of 158 on placebo caught a cold (relative risk 0.69, 95% CI 0.34 to 1.39), which could easily be chance. Cooked or standardised products are the only ones to consider, as raw berries, leaves and stems are toxic.
Key facts about immunity
- In the US, flu caused an estimated 9.4 million to 51 million illnesses, 120,000 to 710,000 hospital stays and 6,300 to 52,000 deaths a year between 2010 and 2025.8
- US adults catch an average of two to three colds a year and children often more, which makes colds one of the most frequent reasons for missed school and work.9
- When 164 healthy US adults were given a cold virus, those who had slept 5 to 6 hours a night in the week before had about 4.2 times the odds of catching a cold of those who slept more than 7 hours.5
- Among 1,002 US adults followed through autumn and winter, those who did aerobic exercise on 5 or more days a week had 43% fewer days with a cold or other upper respiratory infection than those who were largely sedentary.10
- Teaching people about handwashing cuts respiratory illnesses such as colds by 16% to 21% in the general population.11
- Worldwide in 2025, 13.5 million children received no vaccines at all, while about 85% of infants (110 million) had all three doses of the diphtheria, tetanus and whooping cough vaccine.12
Talk to a doctor first if…
Who should avoid
- Daisy-family allergy: avoid echinacea. Ask first if you have hay fever, asthma or eczema.
- Elderberry: never eat raw or unripe elderberries, leaves or stems.
- Echinacea: the EU regulator does not recommend it for autoimmune disease, weakened immunity or children under 12.
- Quercetin: best avoided in kidney disease and hormone-sensitive cancer (animal data), and in pregnancy, where there are no safety data.
- Vitamin C: keep it under 1 g a day. More causes diarrhoea and stomach pain, and men with past kidney stones were linked to more stones with supplements of 1 g a day or more.
Known interactions
- Echinacea and immunosuppressants (severity 2): NCCIH and the EU regulator advise against combining them for theoretical reasons, though no clinical harm is documented in the sources we read.
- Vitamin C and warfarin (severity 1, monitor): large doses of vitamin C may block the action of warfarin, though the evidence is controversial.
- Quercetin: reported to change how some medicines are absorbed, without the drugs being named, so ask a pharmacist if you take regular medication.
- Elderberry: no source we opened names an interaction.
Before you reach for an ingredient
Better-tested measures than any supplement here are washing your hands and getting enough sleep. Both are about lowering the chance of catching an infection, which is what most "immune boosting" claims are really after.
- Hand hygiene modestly lowers the risk of respiratory illness: a Cochrane review of 19 trials found about 11% fewer respiratory illnesses (low-certainty evidence), and 14% fewer acute respiratory infections in nine trials (moderate certainty). It made little or no clear difference to laboratory-confirmed influenza.4
- Short sleep was linked to catching colds: in 164 healthy adults exposed to a cold virus, those who slept under 5 hours or 5 to 6 hours a night were around four times as likely to develop a cold as those sleeping more than 7 hours. It is a single study with a modest sample, so treat it as a reason to protect your sleep rather than a guarantee.5
- The NHS advice for avoiding colds is washing hands with warm water and soap, not sharing towels or cups with someone who has one, not touching your eyes or nose, and staying fit and healthy. It says there is little evidence that vitamin C, echinacea or garlic prevent colds.6
Questions people ask
Can any supplement boost your immune system?
Not in a way the evidence supports. For the options on this page, the best result is a small, uncertain reduction in colds from echinacea, and the Cochrane review could not confirm it. A healthy immune system is not something the trials here show can be made stronger with a supplement.
Does echinacea prevent colds?
Not reliably. The 2014 Cochrane review found no statistically significant effect in any prevention comparison, and the authors called the hint of a 10% to 20% reduction of questionable clinical relevance. Results depend on the species, plant part and preparation, so one product's trial does not vouch for another.
Does elderberry stop you catching colds or flu?
There is no good evidence that it does. The systematic review concluded elderberry may not reduce the risk of developing a cold, and the small trials that suggest it shortens illness were mostly funded by the makers of the product tested. It is not shown to prevent illness.
Does vitamin C prevent colds?
Not for most people. In 10,708 people in general-community trials, regular vitamin C gave a risk ratio for catching a cold of 0.97 (95% CI 0.94 to 1.00), which is no meaningful prevention, while in 598 marathon runners, skiers and soldiers on subarctic exercises it was 0.48.
The Cochrane authors conclude routine supplementation is not justified, and the NHS says there is little evidence that vitamin C prevents colds.
Sources (12)
- Cochrane review Karsch-Völk M, Barrett B, Kiefer D, Bauer R, Ardjomand-Woelkart K, Linde K. Echinacea for preventing and treating the common cold. Cochrane Database Syst Rev. 2014.
- Regulator/health agency NCCIH. Echinacea: Usefulness and Safety. National Center for Complementary and Integrative Health.
- Systematic review Wieland LS, Piechotta V, Feinberg T, et al. Elderberry for prevention and treatment of viral respiratory illnesses: a systematic review. BMC Complement Med Ther. 2021.
- Cochrane review Jefferson T, Dooley L, Ferroni E, et al. Physical interventions to interrupt or reduce the spread of respiratory viruses. Cochrane Database Syst Rev. 2023.
- Experimental study Prather AA, Janicki-Deverts D, Hall MH, Cohen S. Behaviorally Assessed Sleep and Susceptibility to the Common Cold. Sleep. 2015.
- Health service guidance NHS. Common cold. National Health Service (page last reviewed 22 March 2024).
- Systematic review Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013.
- Regulator/health agency CDC. About Estimated Flu Burden. Centers for Disease Control and Prevention (page updated 25 February 2026).
- Regulator/health agency CDC. About Common Cold. Centers for Disease Control and Prevention (page updated 19 February 2026).
- Prospective cohort study Nieman DC, Henson DA, Austin MD, Sha W. Upper respiratory tract infection is reduced in physically fit and active adults. Br J Sports Med. 2011.
- Regulator/health agency CDC. Handwashing Facts. Centers for Disease Control and Prevention (page updated 17 April 2024).
- International health agency World Health Organization. Immunization coverage (fact sheet). 15 July 2026.
Reviewed by Healthy and Herbal editors · 10 October 2026 · Next review April 2027
Reader notes
Experiences and questions from readers, read by an editor before they appear. They are personal accounts, not evidence, and are not medical advice.