Is garlic good for colds? Exploring the science and truth behind the natural remedy

November 23, 2025 •

5 min read

With adults experiencing two to four colds annually on average, many turn to traditional remedies like garlic for relief. But is garlic good for colds, and what does the science actually say about its effectiveness for prevention and treatment?

Quick Summary

Garlic contains the compound allicin, which has antiviral properties that may boost immune function. While some studies suggest it can reduce cold frequency and severity, robust clinical evidence is limited. Proper preparation, like crushing raw garlic, maximizes its benefits.

Key Points

Allicin Activation: Crushing raw garlic releases allicin, the key compound with antiviral properties, and letting it sit for 10-15 minutes maximizes its potency before consumption.
Limited Prevention Evidence: A single, older study suggests daily garlic supplements might reduce the number of colds, but more robust research is needed to validate this finding.
Reduced Symptom Severity: Research on aged garlic extract indicates it may help lessen the severity and duration of cold and flu symptoms, even if it doesn't prevent the illness entirely.
Preparation Matters: Consuming garlic raw or using aged supplements is the most effective way to gain immune benefits, as high heat can destroy the active alliinase enzyme.
Safe for Most: While generally safe in dietary amounts, high doses or supplements can cause side effects like digestive upset and should be discussed with a doctor, especially if taking blood thinners.
Not a Cure: Garlic should be considered a supportive supplement to a healthy lifestyle, not a definitive cure for the common cold.

The History of Garlic as a Natural Remedy

For centuries, people have relied on garlic for its culinary and medicinal properties. From ancient Egyptian texts to Sumerian clay tablets, there are references to garlic being used for health purposes. This long history of use has fueled the popular belief that it can effectively combat the common cold and other infections. Ancient civilizations prized it for everything from treating infections to increasing the work capacity of laborers. Modern research has confirmed some of garlic's wider health benefits, including positive impacts on heart health and antioxidant properties, but its specific effectiveness for the common cold remains a topic of scientific investigation.

The Science Behind Garlic's Immune Support

Garlic's immune-boosting potential is primarily attributed to a compound called allicin. When raw garlic is crushed, chopped, or chewed, an enzyme called alliinase converts alliin into allicin. This unstable, sulfur-containing compound is responsible for garlic's pungent aroma and many of its bioactive effects.

Allicin and Antiviral Properties

Laboratory studies have shown that allicin possesses antimicrobial, antifungal, and antiviral properties. Some research suggests that these compounds may help inhibit viruses, including those responsible for the common cold, from entering and replicating within host cells. However, it's crucial to note that laboratory studies (in vitro) do not always translate directly to clinical efficacy in humans (in vivo).

Boosting the Immune Response

Beyond its direct effect on viruses, garlic is also thought to modulate the immune system. Its compounds have been shown to increase the activity of certain white blood cells, such as natural killer cells, which are part of the body's disease-fighting response. It may also reduce inflammatory cytokines, the chemical messengers that can worsen cold symptoms.

Clinical Research: What Do Studies Show?

Clinical evidence on garlic's effectiveness against the common cold is limited but offers some intriguing findings:

The Josling Study (2001): A double-blind, placebo-controlled survey found that participants taking a daily allicin-containing garlic supplement over a 12-week period had significantly fewer colds (24 cases versus 65 in the placebo group). The total number of days of illness was also lower for the garlic group. However, the time it took to recover once a cold was contracted was similar between both groups.
Cochrane Review (2014): A systematic review analyzed the available evidence and included the Josling study. The authors concluded that while the single trial suggested a potential preventative effect, there was insufficient clinical evidence overall to recommend garlic supplements for preventing or treating the common cold. They emphasized that more rigorous studies are needed to confirm these findings.
Aged Garlic Extract (AGE) Study (2012): Another randomized controlled trial comparing Aged Garlic Extract (AGE) to a placebo found no significant difference in the incidence of colds. However, participants in the AGE group reported fewer and less severe cold and flu symptoms. This suggests AGE might help reduce the severity of illness, even if it doesn't prevent it entirely.

How to Use Garlic for Cold Prevention and Relief

If you choose to use garlic to support your health during cold season, preparation is key to maximizing its benefits:

Activate Allicin: Crush or chop garlic and let it stand for 10-15 minutes before cooking. This allows the alliinase enzyme time to convert into allicin. Excessive heat can inactivate alliinase, so add garlic towards the end of cooking or consume it raw.
Eat It Raw: Eating raw, crushed garlic is often suggested for its high allicin content. You can mix it with honey to make it more palatable.
Create a Garlic Tea: For a soothing remedy, mash garlic with ginger, cloves, and lemon, and steep in hot water. Honey can be added to taste.
Try Fermented Honey Garlic: Peel and lightly crush garlic cloves, then submerge them in raw honey in a glass jar. Let the mixture ferment for a few weeks, periodically releasing pressure. The resulting tonic can be taken by the spoonful.
Consider Aged Garlic Extract: As an alternative for those who dislike the taste or side effects of raw garlic, supplements like AGE have shown some promise in reducing symptom severity.

Raw Garlic vs. Supplements: A Comparison

To help decide the best option, here is a breakdown of different garlic forms and their properties.


Feature	Raw Garlic	Aged Garlic Extract (AGE)	Garlic Powder/Pill
Active Compound	High allicin potential when crushed	Contains other beneficial sulfur compounds (not allicin)	Allicin potential varies; often uses special coating
Taste/Odor	Very pungent, strong odor and flavor	Milder, lacks the strong odor of fresh garlic	Less potent, little to no odor
Absorption	Best absorbed when crushed and left to sit	Stable compounds are more readily absorbed over time	Depends on formulation; some have enteric coatings
Benefit Profile	Best for immediate immune boost due to allicin	May reduce symptom severity and provide antioxidant benefits	Varies widely in potency; effectiveness is uncertain
Side Effects	Bad breath, body odor, digestive issues possible	Generally well-tolerated	Digestive upset can occur

Considerations and Potential Side Effects

While adding garlic to your diet is generally safe for most people, there are important considerations:

Digestive Issues: Some individuals, especially those with irritable bowel syndrome (IBS), may find that garlic worsens stomach discomfort, bloating, or diarrhea.
Medication Interactions: High doses of garlic, particularly from supplements, can interact with blood-thinning medications like warfarin, increasing the risk of bleeding. If you are on medication, consult a healthcare provider before increasing your garlic intake.
Allergies: Garlic allergies can occur and manifest as respiratory or skin symptoms.
Topical Use: Applying raw garlic directly to the skin can cause a burning sensation and irritation.

Conclusion: A Supportive Supplement, Not a Cure

So, is garlic good for colds? While the idea of a simple cure is appealing, the scientific evidence is more nuanced. Garlic, particularly in its raw form or as an Aged Garlic Extract, contains powerful compounds that can support the immune system and may help reduce the frequency or severity of colds. However, it is not a guaranteed cure and should not replace proper medical advice for serious infections. As a natural supplement to a healthy lifestyle that includes proper nutrition, hydration, and rest, garlic can be a valuable addition to your cold and flu season toolkit.

For more detailed information on the research surrounding garlic and the common cold, consult the systematic review by Cochrane: Garlic for the common cold - PMC

Frequently Asked Questions

Eating raw, crushed garlic is believed to be the most potent method for receiving its immune-boosting benefits, as this process releases the active compound allicin. However, the evidence on its effectiveness in treating or preventing colds is limited.

Research from a 2001 study showed that while daily garlic supplements reduced the number of colds, the length of a cold once contracted was similar to the placebo group. More recent studies on Aged Garlic Extract suggest it may reduce the severity of symptoms, but not necessarily the overall duration.

No. The enzyme alliinase, which produces the immune-boosting compound allicin, is sensitive to heat and can be inactivated by cooking. To maximize benefits, crush garlic and let it sit for 10-15 minutes before adding it to recipes or consume it raw.

Aged garlic extract (AGE) is a type of garlic supplement that does not contain allicin but retains other beneficial compounds. Some studies on AGE show it can reduce the severity of cold symptoms, offering an alternative for those who dislike raw garlic's strong taste.

Yes. Potential side effects include bad breath, body odor, and digestive issues like bloating or stomach upset. High doses or supplements can also interact with blood-thinning medications.

There is no universally recommended dose for immune support. While some research has used specific amounts in studies, it's generally best to incorporate garlic into your diet in amounts you tolerate well.

Honey should not be given to children under the age of two. For older children and general concerns about using garlic, it is best to consult a healthcare provider to ensure it is appropriate and to determine a safe dosage.

Yes, mixing crushed raw garlic with honey can create a soothing syrup that combines garlic's immune properties with honey's throat-soothing effects. This is a popular home remedy for coughs and sore throats.