16 Major Garlic Side Effects

Garlic contains sulfur compounds called thiosulfinates, which are responsible for many of garlic’s health benefits. But excessive consumption of garlic can cause side effects like nausea, vomiting, diarrhea, abdominal pain, dizziness, headache, skin rashes, and breathing difficulties.

According to WebMD, some people even suffer from allergic symptoms after consuming garlic. These include asthma attacks, hives, itching, swelling, and difficulty swallowing. In addition, garlic can increase the risk of developing anemia, which reduces the number of red blood cells in the body.

Side Effects of Garlic 

Garlic is considered a superfood because of its many health benefits. It helps lower cholesterol levels, fights cancer, reduces blood pressure, and even protects against heart disease. However, there are side effects associated with consuming too much garlic. Here are the common ones.

garlic side effects

1. May Cause Bad Odor

Garlic is good for health. It helps lower cholesterol levels, fights cancer, protects against heart disease, boosts immunity, reduces blood pressure, and even prevents strokes. But there are some downsides to eating too much of the pungent bulb. One of those downsides is the odor. If you eat garlic raw, it gives off a strong odor that lingers in the mouth. This is called “garlic breath.” Garlic breath isn’t necessarily a problem, though. You just need to know how to deal with it.

There are certain chemicals in garlic — such as allicin and thiosulfinates — that cause bad breath. These compounds break down into sulfurous gases that emit foul odors. When you chew garlic, you release these sulfur-containing molecules into the air. So, if you’re chewing gum while talking to someone, chances are he’ll notice your garlic breath.

To avoid this issue, try eating your garlic cooked. Cooked garlic doesn’t produce as many volatile sulfur compounds, so the odor won’t linger as long. Also, don’t use garlic breath spray. Spraying the stuff on your tongue will actually increase the amount of garlic breath because it coats the surface where the odor is produced. Instead, brush your teeth after eating garlic. Brush your teeth twice daily to ensure that you keep your breath clean.

2. May Cause Liver Damage

Consuming large amounts of raw garlic can lead to liver damage. This happens because the compound called allicin, found in garlic, causes the body to produce enzymes that break down proteins. When this occurs, it leads to inflammation of the liver cells, which can eventually turn into scar tissue. This can make the organ function less efficiently and increase the risk of developing cirrhosis.

3. May Cause Heartburn

The compounds in garlic known as thiosulfinates can irritate the stomach lining, causing acid reflux. If this continues over a long period of time, it can lead to ulcers and esophageal cancer.

4. May Drop Blood Pressure

Garlic lowers blood pressure too much, especially in people taking blood pressure medicine. It can lower blood pressure enough to make some patients stop taking their medications. This is why doctors usually recommend against giving up blood pressure drugs just because you eat lots of garlic.

The supplement form of garlic is generally considered safer than eating raw garlic cloves. But there are still risks involved. If you decide to try the supplement form of garlic, start out slowly and work your way up to larger doses over several weeks. You might even want to talk to your doctor about how to safely use garlic supplements.

5. May Cause Nausea, Vomiting, And Heartburn

Garlic may cause heartburn, nausea, and vomiting if taken too much or too often. If you are pregnant, consult with your doctor before including garlic to your diet.

6. May Cause Gastric Issues

Garlic is one of those foods that people love to eat because it tastes good and is full of nutrients. But there are some things you should know about eating garlic. First off, it contains sulfur compounds called thiosulfinates and allicin, which give garlic its characteristic odor and flavor. 

These chemicals irritate the mucous membranes of the mouth and throat, causing them to swell up and become irritated. This irritation causes pain and burning sensations, and sometimes even leads to ulceration or bleeding in the esophagus, stomach, or duodenum.

There is no scientific evidence linking the consumption of garlic to the prevention of gastric cancer or gastritis. However, there is some evidence suggesting that garlic may prevent Helicobacter pylori infections. 

pylori is a bacterium that infects the stomach and causes gastritis, peptic ulcers, and gastric cancer. Studies show that garlic supplements reduce the risk of developing H. pylori infection.

7. May Aggravate Bleeding

Garlic contains compounds called thiosulfinates, which are known to increase platelet aggregation and interfere with blood clotting. A study published in the Journal of the American Medical Association found that people who ate about half a clove per day had twice the risk of developing heart disease compared to those who did not eat it.

 Other studies show that garlic can cause bleeding problems including nosebleeds, gums bleeds, and gastrointestinal bleeding. If you’re taking blood thinners such as warfarin (Coumadin), aspirin, or heparin, avoid eating garlic because it could make you bleed more easily.

8. May Induce Sweating

Garlic contains compounds called thiosulphates that trigger sweating. This happens because it activates sweat glands in the skin. Thiosulphinates are found in many plants including onions, leeks, chives, garlic, and fennel. They are also present in some foods such as cabbage, cauliflower, broccoli, Brussels sprouts, and kale. These compounds cause sweating when taken orally. However, they do not cause sweating when applied to the skin.

The amount of sweating induced varies depending on how much you eat. For example, eating one clove of raw garlic once every day could induce sweating. Eating three cloves daily might make you feel hot and sweaty. Cooking the garlic reduces the amount of sweating that occurs when you consume it.

9. May Cause Dizziness

Garlic contains a chemical called allicin, which activates the trigeminal nerve. This can cause headaches, dizziness, nausea, and vomiting. If you are prone to migraines, it might be best to steer clear of garlic.

10. May Cause Headache

Garlic is known to cause headaches, but it could be worse than you think. Raw garlic activates the trigeminal nerve and triggers migraines. 

A study published in the Journal of Neurology found that raw garlic is linked to migraine attacks. In addition to triggering migraines, garlic can also cause nausea, vomiting, dizziness, and tingling sensations.

11. May Aggravate (Vaginal) Yeast Infection

Garlic is often used to treat vaginal yeast infections because it contains antifungal properties. However, women should avoid inserting garlic cloves inside their vaginas because doing so could make an existing infection worse.

A study published in the journal Fertility and Sterility found that women who ate garlic regularly had a greater risk of developing a vaginal yeast infection. Researchers analyzed data from 2,816 women enrolled in the National Health and Nutrition Examination Survey III. They found that women who used one clove of raw garlic per day had a 40 percent increased risk of developing vaginal candidiasis compared with those who did not eat garlic.

The researchers theorized that the high sulfur compounds in garlic might contribute to the development of vaginal infections. When the body encounters a foreign substance like food, it produces antibodies to fight off the invasion. If the immune system fails to recognize the invader, it releases histamines to attack the intruder. Histamine causes itching and redness around the area where the garlic was eaten or used. This response is what leads to the symptoms associated with a vaginal yeast infection.

In addition to causing itching and burning, eating garlic can lead to stomach upset. A woman who eats garlic should drink plenty of fluids to prevent dehydration. She should also use a tampon during her menstrual period to catch any blood flow that gets out of control.

12. May Cause Vision Changes

Garlic may cause hyphema, which is blood in the eye. Hyphema is usually caused by trauma to the eye, such as a blow to the head or injury during surgery. A person who eats too much garlic might develop hyphema due to increased pressure inside the eyeball. This can lead to temporary vision changes. If you experience sudden blurred vision, it is important to see a doctor immediately.

13. May Causes Skin Irritation And Allergies

One of the most common symptoms associated with garlic consumption is skin irritation or rashes. Some people report itching and burning sensations while others experience redness, swelling, and blisters. These symptoms usually go away within 24 hours, but some people do develop longer-lasting issues such as hives or psoriasis.

14. Is An Allergen

While garlic is generally considered safe for most people, it does contain allergens that can trigger allergic reactions. If you suffer from asthma, food allergies, or hay fever, you might want to avoid eating too much garlic because it can worsen your symptoms.

15. Can Be Dangerous For Pregnant Women

If you are pregnant or breastfeeding, you should limit your intake of garlic. Studies show that consuming large amounts of garlic during pregnancy can lead to low birth weight babies. This is due to the way garlic works in the body; it increases levels of prostaglandins, hormones that help regulate blood pressure and contractions. Too high of a level of prostaglandins can increase the risk of miscarriage.

16. Garlic During Pregnancy & Breastfeeding

Garlic oil is safe to consume while you are pregnant or breastfeeding. This includes garlic supplements, such as capsules, tablets or liquids. You do not want to take too much garlic because it could cause problems for your baby. If you are taking garlic pills, make sure to check the ingredients list to ensure there is no alcohol or caffeine in the product. Alcohol and caffeine are both harmful to babies.

If you are breastfeeding, you do not want to eat raw garlic cloves. Raw garlic contains high amounts of sulfur compounds that can damage your milk supply. However, cooked garlic is fine to consume while you are breastfeeding.

17. Garlic And Drug Interactions

Garlic has been used for thousands of years as medicine. It has been shown to help treat everything from high blood pressure to heart disease. But did you know garlic can interact with certain drugs? Here are some things to keep in mind about how garlic interacts with prescription medications.

  • Garlic Interaction with Cytochrome P450 2E1 (CYP2E1) substrates

Some medications are changed and broken down by the liver. CYP2E1 is one such enzyme. CYP2E is responsible for metabolizing many drugs, including antibiotics, antihistamines, antidepressants, antipsychotics, antiepileptics, and painkillers. When you eat garlic, it increases the activity of CYP2E1, meaning that the body breaks down certain medications faster. This could mean that the medication takes longer to work, or that you take too much of it.

Garlic contains compounds called thiosulfinates, which increase the activity of CYP enzymes. Thiosulfinates help the body break down chemicals found in pesticides, herbicides, fungicides, and insecticides. They also prevent cancer cells from multiplying. In addition, thiosulfinates stimulate the immune system and fight bacteria.

When taken together, garlic and medications can cause serious problems. For example, taking both aspirin and garlic can lead to bleeding. Taking both clopidogrel (Plavix) and garlic can lead to low blood pressure. If you take both warfarin (Coumadin) and garlic, you may experience excessive bleeding.

If you take medications, talk to your doctor about whether eating garlic affects your prescription.

Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates) interact with GARLIC

Garlic is known to inhibit the activity of Cytochrome P450 enzymes (CYPs). These are the proteins responsible for metabolizing many medications. When garlic is taken together with certain medications, it increases the amount of drug that stays in the body longer. 

This can lead to side effects such as nausea, diarrhea, headaches, dizziness, insomnia, and heartburn. 

If you take both garlic and a medication that is broken down by CYP3A4, you may experience increased levels of the active ingredient. You may want to avoid taking garlic while taking medications that are broken down by CYP 3A4.

  • Warfarin (Coumadin) interacts with GARLIC

The combination of garlic and Coumadin (warfarin) can cause bleeding problems. Garlic contains compounds called thiosulfinates that are similar to those found in Coumadin. Thiosulfinates react with proteins in the body, including vitamin K-dependent factors such as prothrombin and factor VII. When these proteins become inactive, it causes excessive bleeding.

Garlic also contains another compound called allicin that reacts with iron in the stomach. Allicin forms insoluble complexes with iron, causing gastrointestinal distress. If you take both garlic and Coumadin together, you could experience severe gastrointestinal symptoms, including diarrhea, nausea, vomiting, abdominal pain and rectal bleeding.

If you think you’ve had a reaction to garlic, contact your physician immediately.

  • Medications for high blood pressure (Antihypertensive drugs) interact with GARLIC

Garlic extract lowers cholesterol levels in people with elevated cholesterol. A study published in the Journal of Nutrition found that taking garlic extract supplements for six weeks had significant effects on reducing total cholesterol and LDL cholesterol levels in participants with high cholesterol.

Blood pressure is lowered in those taking garlic extract. In another study, researchers investigated whether garlic could lower systolic blood pressure (the top number) and diastolic blood pressure (the bottom number). They found that garlic extract did lower both numbers in patients with hypertension, although it didn’t affect healthy individuals.

More research needs to be done to determine if garlic extract will help prevent cardiovascular diseases like stroke and heart attack.

Special Precautions and Warnings

Raw garlic is probably unsafe when used on the human body. Ingestion of raw garlic can lead to gastrointestinal distress, including nausea, vomiting, diarrhea, abdominal pain, and even ulcers. Garlic is known to slow down blood flow and increase platelet aggregation, both of which can potentially lead to bleeding. Taking garlic orally might also cause stomach upset, heartburn, or other digestive problems.

Children should avoid large amounts of raw garlic because of the risk of choking or aspiration. Pregnant women and people who take blood-thinning drugs or other medications that affect coagulation should talk to their doctors before consuming garlic. Applying raw garlic directly to the skin can cause an allergic reaction in some people. If you use garlic oil, make sure to dilute it with olive oil or another carrier oil.


In conclusion, garlic has many uses besides cooking. Garlic is also used for medicinal purposes, including treating high blood pressure, lowering cholesterol levels, preventing cancer, and reducing inflammation. But despite its many benefits, garlic does have drawbacks. For example, garlic may cause allergic reactions in some individuals. Also, if you take too much garlic, you might notice a bad taste in your mouth. And finally, garlic isn’t recommended during pregnancy because of possible risks to the fetus.

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