Garlic is one of the most popular ingredients in kitchens around the world. It adds flavor to meals and has also been used traditionally for various health purposes. Because garlic is often described as a “natural remedy,” it is easy to assume that consuming more of it must always be better.
But can garlic cause side effects?
Yes. For most people, garlic is safe when eaten in normal food amounts. However, eating large amounts of raw garlic or taking concentrated garlic supplements can cause unpleasant effects and may interact with certain medicines. Common problems include bad breath, body odor, heartburn, stomach upset, abdominal pain, gas, and nausea. Some people can also have an allergic reaction to garlic.
This guide explains the most common garlic side effects, who should be more cautious, possible garlic and medication interactions, and when it may be appropriate to speak with a healthcare professional.
What Is Garlic?
Garlic, scientifically known as Allium sativum, is a plant related to onions, leeks, and shallots. It has been used as both a food and traditional health product for centuries.
Today, garlic is available in many forms, including fresh cloves, cooked garlic, raw garlic, garlic powder, aged garlic extracts, oils, and dietary supplements.
The amount and form matter when considering side effects. A small amount of garlic used to season food is very different from taking a concentrated garlic supplement.
According to the National Center for Complementary and Integrative Health (NCCIH), garlic is generally considered safe for most people when consumed in the amounts normally found in food. However, supplements may have stronger effects and may carry additional risks.
Common Garlic Side Effects
Most garlic side effects are mild and involve digestion, taste, or body odor. They may be more noticeable after eating large quantities or consuming raw garlic.
1. Bad Breath
One of the best-known side effects of garlic is bad breath.
Garlic contains sulfur-containing compounds that can contribute to its strong smell. Some of these compounds can remain in the body after digestion, which is why brushing your teeth alone may not completely remove garlic breath.
For most people, garlic breath is inconvenient rather than dangerous.
2. Body Odor
Garlic can also affect body odor.
The same compounds responsible for garlic's distinctive smell can contribute to an odor that some people notice after eating garlic. The effect varies from person to person and may depend on how much garlic is consumed.
3. Heartburn and Acid Reflux
Garlic may cause heartburn or make digestive discomfort worse in some people.
This can be particularly noticeable after eating raw garlic or large amounts of garlic. People who already experience acid reflux may find that certain garlic-heavy meals trigger symptoms.
If you repeatedly notice burning in your chest or upper abdomen after eating garlic, consider discussing the symptoms with a healthcare professional rather than assuming garlic is the only possible cause.
4. Stomach Upset
Eating a lot of garlic can cause stomach discomfort.
Possible symptoms include:
Abdominal pain
Nausea
Gas
Bloating
Heartburn
Burning in the mouth or stomach
NCCIH lists abdominal pain, flatulence, nausea, breath odor, and body odor among possible side effects of garlic taken orally.
Large amounts of garlic may also cause burning sensations in the mouth, esophagus, and stomach.
5. Nausea
Some people feel nauseated after consuming large amounts of garlic, particularly raw garlic or concentrated garlic preparations.
If nausea occurs consistently after eating garlic, reducing the amount may help. Persistent nausea, however, should not automatically be blamed on garlic because many other digestive and medical conditions can cause it.
6. Gas and Bloating
Garlic can cause gas or bloating in some people.
Digestive reactions differ considerably between individuals. Someone may eat garlic regularly without any problem, while another person may experience significant discomfort after a relatively small amount.
If garlic repeatedly causes digestive symptoms, keeping a simple food diary can help identify whether garlic is actually the trigger.
Can Raw Garlic Cause More Side Effects?
Raw garlic can be particularly strong.
Some people tolerate cooked garlic but experience heartburn, stomach irritation, or burning after eating raw garlic. Raw garlic can also produce a stronger smell.
This does not mean raw garlic is automatically harmful. Rather, the form and quantity can affect how an individual responds.
It is also important to distinguish eating raw garlic from applying raw garlic directly to the skin.
Do not assume that because garlic is safe to eat, it is safe to apply directly to your skin. NCCIH warns that fresh raw garlic applied to the skin can cause severe irritation and chemical burns.
Garlic and Bleeding Risk
One of the more important concerns involves garlic supplements and bleeding.
Garlic may affect blood clotting, and concentrated garlic supplements may increase bleeding risk. This is especially important for people taking medicines that already affect blood clotting.
For example, caution is warranted for people taking anticoagulants or antiplatelet medicines. NCCIH specifically advises people taking anticoagulants, aspirin, or other medicines to discuss garlic and other herbal products with a healthcare professional.
This concern is generally more relevant to concentrated supplements than the small amounts of garlic normally eaten as part of a meal. MSD Manual notes that ordinary dietary amounts are unlikely to cause significant drug interactions, while larger supplemental amounts can interact with medicines such as warfarin.
Garlic Before Surgery or Dental Procedures
If you regularly take garlic supplements, tell your doctor or dentist before a planned procedure.
Because concentrated garlic products may affect bleeding, healthcare professionals may recommend stopping certain supplements before surgery or dental procedures. The appropriate timing depends on the product, procedure, and person's medical circumstances.
Do not stop a prescribed blood-thinning medicine on your own simply because you are concerned about garlic. Medication changes should be discussed with the healthcare professional who prescribed the medicine.
Garlic and Medication Interactions
Garlic supplements can interact with some medicines.
Potential interactions include medicines that affect:
Blood Clotting
Garlic may increase bleeding risk when combined with anticoagulant or antiplatelet medicines.
Examples include warfarin and some other medicines that reduce blood clotting.
Blood Pressure
Garlic may have a modest blood-pressure-lowering effect. Combining concentrated garlic products with blood-pressure medicines could potentially lower blood pressure too much in some people.
Blood Sugar
Garlic may have a small blood-sugar-lowering effect. Using concentrated garlic supplements alongside medicines for diabetes could potentially contribute to blood sugar becoming too low.
Certain HIV Medicines
Garlic has been reported to interfere with the effectiveness of some HIV medicines, including saquinavir.
Tacrolimus
Garlic may also interact with tacrolimus, a medicine used to help prevent organ-transplant rejection. MSD Manual notes that this interaction may increase tacrolimus levels and potentially contribute to liver injury.
Because medication interactions can be complicated, anyone taking regular prescription medicines should check with a pharmacist or doctor before starting a concentrated garlic supplement.
Can You Be Allergic to Garlic?
Yes. Although garlic allergy is uncommon, some people can have an allergic reaction.
Possible symptoms of a food allergy may include itching, hives, swelling, vomiting, or breathing difficulties.
A suspected serious allergic reaction requires urgent medical attention. Difficulty breathing, swelling of the lips or tongue, fainting, or rapidly worsening symptoms should be treated as an emergency.
NCCIH confirms that some people can have allergic reactions to garlic.
Garlic Side Effects in Pregnancy and Breastfeeding
Garlic used as a normal food ingredient is different from taking large amounts as a supplement.
NCCIH states that garlic may not be safe during pregnancy or breastfeeding when taken orally in amounts greater than those normally found in food. There is also limited information about topical garlic use during pregnancy and breastfeeding.
If you are pregnant or breastfeeding and are considering a garlic supplement, speak with your healthcare professional before taking it.
Who Should Be Careful With Garlic Supplements?
Garlic supplements deserve more caution than ordinary dietary garlic.
You should consider talking to a healthcare professional before using a garlic supplement if you:
Take blood thinners or antiplatelet medicines
Take blood-pressure medication
Take diabetes medication
Take HIV medication
Take tacrolimus or other transplant medicines
Have a bleeding disorder
Are preparing for surgery or a dental procedure
Are pregnant or breastfeeding
Have previously experienced an allergic reaction to garlic
This does not mean these people can never eat garlic. The important issue is that food amounts and concentrated supplements are not necessarily equivalent.
Is Garlic Safe to Eat Every Day?
For most healthy people, garlic eaten as part of a normal diet is generally considered safe.
The key is moderation.
There is no need to consume large quantities of raw garlic simply because garlic has a reputation for being healthy. More is not necessarily better, particularly when it causes digestive symptoms or when a concentrated supplement is involved.
NCCIH reports that garlic has been used safely in research studies lasting as long as seven years, although safety can vary according to the preparation and how it is used.
Are Garlic Supplements Better Than Fresh Garlic?
Not necessarily.
Garlic supplements contain different preparations and concentrations, and research does not mean that every garlic product provides the same effects.
Some studies suggest garlic supplements can produce modest reductions in total cholesterol and LDL cholesterol, and there is limited evidence that they may modestly lower blood pressure in people with high blood pressure.
However, these potential benefits should not be interpreted as proof that everyone needs a garlic supplement.
For most people, using garlic as part of a balanced diet is a straightforward way to enjoy its flavor without deliberately taking large doses.
How to Reduce Garlic Side Effects
If garlic causes mild digestive discomfort, several practical approaches may help:
Use smaller amounts. Eating less garlic may reduce symptoms.
Try cooked garlic. Some people find cooked garlic easier to tolerate than raw garlic.
Avoid very concentrated products. Garlic supplements can provide substantially more concentrated amounts than ordinary food.
Pay attention to your symptoms. If garlic consistently causes heartburn, stomach pain, or nausea, consider reducing your intake and discussing persistent symptoms with a healthcare professional.
Check your medicines. If you take prescription or over-the-counter medicines regularly, ask a pharmacist about potential interactions before starting a garlic supplement.
Garlic Side Effects vs. Garlic Benefits
Garlic is sometimes promoted online as a cure-all for conditions ranging from infections to cancer. The evidence is more complicated.
Research suggests that garlic supplements may have modest effects on certain cardiovascular risk factors, including cholesterol and blood pressure. However, evidence does not support assuming that garlic supplements can prevent or treat every disease for which they are promoted.
For example, NCCIH reports that there is not enough evidence to determine whether garlic prevents or treats the common cold, and garlic consumption has not been shown to reduce stomach cancer risk.
This distinction matters when evaluating health information online. A food can be nutritious and useful without being a replacement for medical treatment.
When Should You Stop Taking Garlic?
If garlic causes mild symptoms such as temporary gas or heartburn, reducing your intake may be reasonable.
However, seek professional medical advice if you experience:
Persistent or severe abdominal pain
Repeated vomiting
Unusual or significant bleeding
Severe dizziness or weakness
Signs of an allergic reaction
Difficulty breathing
Swelling of the lips, tongue, or throat
If you suspect that a medicine and garlic supplement are interacting, contact your doctor or pharmacist rather than simply changing your prescription medication.
Frequently Asked Questions About Garlic Side Effects
What are the most common side effects of garlic?
The most common garlic side effects include bad breath, body odor, heartburn, stomach upset, abdominal discomfort, gas, and nausea. Some people may also experience an allergic reaction.
Does garlic cause stomach problems?
It can. Eating large amounts of garlic, particularly raw garlic, may cause stomach irritation, nausea, abdominal discomfort, heartburn, or burning in the digestive tract.
Can garlic cause bleeding?
Concentrated garlic supplements may increase bleeding risk, particularly when combined with medicines that affect blood clotting. Normal amounts used in food are much less likely to cause significant interactions.
Is raw garlic bad for you?
Raw garlic is not automatically bad for you, but it can be harder for some people to tolerate. It may cause stronger heartburn, stomach irritation, or other digestive symptoms. Raw garlic should also not be applied directly to the skin because it can cause serious irritation and chemical burns.
Can garlic cause an allergic reaction?
Yes. Garlic allergy can occur in some people. Symptoms can range from skin reactions to more serious allergic symptoms.
Should I avoid garlic before surgery?
If you take garlic supplements, tell your healthcare professional before surgery or a dental procedure. Concentrated garlic products may affect bleeding. Do not independently stop prescribed medicines without medical advice.
The Bottom Line
Garlic is generally safe for most people when eaten in ordinary food amounts. However, garlic side effects can occur, especially when large amounts of raw garlic or concentrated garlic supplements are consumed.
The most common problems are digestive discomfort, heartburn, nausea, gas, bad breath, and body odor. More important concerns involve possible bleeding and medication interactions, particularly with garlic supplements.
If you take prescription medicines, have a medical condition, are pregnant or breastfeeding, or are preparing for surgery, talk with a qualified healthcare professional before taking garlic supplements.
Garlic can be a flavorful part of a balanced diet, but “natural” does not automatically mean risk-free. The safest approach is to consider the amount, form, your personal health circumstances, and any medicines you take.
Medical disclaimer: This article is for general educational purposes and is not a substitute for personalized medical advice, diagnosis, or treatment. If you have concerning symptoms or questions about garlic and your medication, speak with a qualified healthcare professional.