Do Immune Boosters Actually Work? A Look at Echinacea and Elderberry

The short answer is: it depends on what you mean by "work," and the evidence is more limited than most product labels suggest. Here is what the science actually shows about two of the most widely used immune-support supplements, echinacea and elderberry, based on data from the NIH Office of Dietary Supplements (ODS) and the National Center for Complementary and Integrative Health (NCCIH).

What Does "Immune Booster" Even Mean?

Neither echinacea nor elderberry is an essential nutrient. Unlike vitamin C or zinc, they have no established dietary requirement, no adult target intake, and no upper limit set by health authorities. They are botanicals, meaning they are plant-derived compounds studied for potential biological activity rather than for correcting a nutritional deficiency. Because of this, the bar for evidence is different, and the research base is still developing.

As a reminder, dietary supplements are not intended to diagnose, treat, cure, or prevent any disease, and these statements have not been evaluated by the FDA.

Echinacea: What the Research Shows

Potential mechanisms

Laboratory research, most of it conducted in cell cultures rather than in people, suggests echinacea may have antioxidant and antibacterial activity. Some in vitro studies suggest it may stimulate monocytes and natural killer cells, which are part of the innate immune response. Other laboratory work suggests certain echinacea compounds might inhibit some viruses from binding to host cells. The ODS notes that most of this evidence comes from in vitro data, meaning results in a lab dish do not always translate to the same effects in a living person.

What clinical evidence says

The ODS and NCCIH grade the human evidence as follows:

• Taking echinacea may slightly reduce the chance of catching a cold. This finding is graded as limited, meaning some studies suggest a benefit but the overall body of evidence is not yet strong enough to draw firm conclusions.
• Whether echinacea shortens the duration of a cold once you have one is graded as insufficient. The available studies do not yet provide reliable answers.
• Whether echinacea reduces the severity of cold symptoms is also graded as insufficient.
• Whether echinacea helps prevent or treat influenza is graded as insufficient.
• Whether echinacea prevents or treats COVID-19 is graded as insufficient.
• Whether echinacea reduces respiratory infections or complications in children is graded as insufficient.

In plain terms, there is a hint of possible benefit for cold prevention, but the evidence is not strong enough to make confident recommendations.

Safety and side effects

NIH sources describe echinacea as likely safe for most adults when taken for short periods as extracts of Echinacea purpurea, or certain E. purpurea combined with E. angustifolia products. Common side effects include abdominal pain, nausea, diarrhea, sleeplessness, and skin rashes. Some people experience allergic reactions that may be severe, particularly people who are allergic to related plants such as ragweed or daisies. Those individuals should be cautious and speak with a clinician before trying echinacea.

Drug interactions

The ODS and NCCIH flag several interaction concerns worth knowing about:

• Immunosuppressant medications: because echinacea may have immunostimulatory activity, it might reduce the effectiveness of drugs that suppress the immune system.
• Drugs metabolized by liver enzymes (cytochrome P450): NCCIH reports conflicting evidence, and the ODS notes echinacea might increase cytochrome P450 activity, potentially lowering the levels of some medications processed by these enzymes.
• Caffeine: NCCIH notes there are theoretical reasons to suspect an interaction between echinacea and caffeine.

NIH advises anyone taking any medication to speak with a health care provider before using echinacea, because some herbs and medicines interact in ways that can be harmful.

Elderberry: What the Research Shows

Potential mechanisms

Elderberry (Sambucus nigra) contains anthocyanins, flavonols, and phenolic acids. Laboratory studies suggest these compounds may have antioxidant activity. Preliminary laboratory and animal research also suggests elderberry constituents might have anti-inflammatory effects and might inhibit some viruses from binding to host cells. As with echinacea, most of this work has not yet been confirmed in large, well-designed human trials.

What clinical evidence says

The ODS and NCCIH grade the human evidence as follows:

• Elderberry supplementation may reduce the severity and duration of the common cold and the duration of flu. This is graded as limited, meaning early findings are somewhat encouraging but the evidence base is not yet sufficient for firm conclusions.
• Whether elderberry reduces the risk of catching the common cold is graded as insufficient.
• Whether elderberry is beneficial for COVID-19 is graded as insufficient.
• Whether elderberry is helpful for health purposes beyond upper respiratory symptoms is graded as insufficient.

Safety: an important warning about raw elderberries

This is one area where the evidence is strong, and the finding is a safety warning rather than a benefit. The bark, leaves, seeds, and raw or unripe fruit of S. nigra contain a cyanogenic glycoside, a compound that can cause nausea, vomiting, diarrhea, dehydration, and cyanide poisoning. Cooking destroys this toxin. Elderberry flowers and properly cooked or processed ripe fruit appear to be safe. If you are considering elderberry, use only commercially processed products or properly cooked preparations, never raw or unripe berries or any part of the bark or leaves.

Drug interactions

The ODS and NCCIH flag the following interaction concerns:

• Immunosuppressant medications: due to its potential immunostimulatory activity, elderberry might reduce the effectiveness of immune-suppressing drugs.
• Diabetes medications and blood glucose control: elderberry might affect insulin and glucose metabolism. People with diabetes or those taking glucose-lowering drugs should use elderberry with caution and consult a clinician first.
• Diuretic drugs: elder flower may have diuretic effects, so caution is advised when combining it with medications that increase urination.

The Bottom Line

Both echinacea and elderberry have some interesting preliminary science behind them, but the honest summary is that human clinical evidence remains limited to insufficient for most of the outcomes people care about, including cold prevention, cold duration, flu, and COVID-19. Neither supplement has a proven required role in human physiology, and neither has an established recommended intake.

If you are generally healthy and considering either supplement for short-term use during cold season, the safety profile appears reasonable for most adults based on current NIH data. However, if you take any prescription or over-the-counter medications, have diabetes, use immunosuppressants, or have plant allergies, please talk with your doctor or pharmacist before adding either supplement to your routine. Personal dosing decisions should always be made with a qualified clinician, not based on a label or a general guide like this one.

Sources

• NCCIH: Echinacea (https://www.nccih.nih.gov/health/echinacea)
• ODS: Dietary Supplements in the Time of COVID-19 (https://ods.od.nih.gov/factsheets/COVID19-HealthProfessional/)
• ODS: Immune Function, Consumer and Health Professional fact sheets (https://ods.od.nih.gov/factsheets/ImmuneFunction-Consumer/)
• NCCIH: The Common Cold and Complementary Health Approaches (https://www.nccih.nih.gov/health/providers/digest/the-common-cold-and-complementary-health-approaches-science)
• NCCIH: Elderberry (https://www.nccih.nih.gov/health/elderberry)
• NCCIH: European Elder (https://www.nccih.nih.gov/health/european-elder)