What Are the Benefits and Risks of Onion Water? How Is It Prepared?

Onions are among the vegetables most commonly used in our kitchens, adding flavor and offering many health benefits. In recent years, onion water regimens have become popular for weight loss, menstrual irregularities, immune support, and even cancer prevention. What benefits does onion water really have, and could regular consumption be harmful? What does scientific research say, particularly about its effects on cancer?

Nutritional Content of Onion Water

Understanding onions' health effects requires knowing their vitamins and minerals. Onions are particularly rich in vitamins A, C, and B and minerals such as calcium, folate, phosphorus, magnesium, potassium, iodine , and sulfur . They also contain abundant flavonoids with strong antioxidant properties, such as quercetin . These nutrients form the basis of onion water's benefits for the body.

The following table summarizes the main nutrients in 100 grams of raw bulb onion:

Straining out the pulp reduces fiber, but most vitamins, minerals, and antioxidants transfer to the water. Onion water can therefore be described as a highly nutritious regimen. Potassium and sulfur compounds play particularly important roles in its health effects.

What Are the Benefits of Onion Water?

Its vitamins, minerals, and bioactive compounds may benefit health in several ways. Traditional experience and scientific data suggest that the main benefits of onion water include:

• Natural Antibiotic and Antioxidant Effects: Quercetin gives onion water strong antioxidant activity, while its natural antibiotic properties protect the body against microbes. It thereby strengthens immunity , increases resistance to infection, and supports the body's defenses by reducing chronic inflammation risk.

• Supports Cardiovascular Health: Onion water may help balance blood sugar, cholesterol, and blood pressure, potentially lowering cardiovascular disease risk. Research suggests that regular onion consumption reduces clot formation through blood-thinning effects and thereby lowers heart attack and stroke risk. Potassium also contributes to blood pressure control.

• Potential Protection Against Cancer: Although certain molecules in onion water are known to have anticarcinogenic properties, these effects have not yet been demonstrated in human clinical trials.

• Removes Toxins and Supports Digestion: Onion water is known to have diuretic and mild laxative effects. This speeds the removal of retained fluid and toxins , producing a kind of detox effect. It is also reported to stimulate stomach enzymes, aid digestion, and regulate bowel movements. Raw onion water may instead cause discomfort in people with sensitive stomachs, so caution is needed (see adverse effects below).

• Helps With Weight Loss: Does onion water help you lose weight? It is widely believed that onion water speeds metabolism and supports weight loss. Taken on an empty stomach, it may indeed increase fat burning and fluid removal. Its nutrients may also promote fullness and balance appetite. However, for healthy weight loss , onion water alone is no miracle; it is a supportive addition to a balanced diet and exercise.

• Regulates Blood Sugar: Its low glycemic content and antioxidants contribute to blood sugar regulation. It is thought particularly to reduce type 2 diabetes risk. Because it lowers blood sugar, however, people taking diabetes medicines should be careful to avoid hypoglycemia (see adverse effects below).

• Improves Skin Health: Onion water's antiseptic and antioxidant properties may benefit the skin. Regular consumption or direct application is reported to reduce acne formation and dry existing pimples. Sulfur and vitamin C may also support collagen production , reducing wrinkles and revitalizing the skin. People with sensitive skin should first test direct application on a small area.

• Reduces Hair Loss: Does onion water promote hair growth? Onion water is traditionally used for hair care. Sulfur compounds and antibacterial properties may nourish the scalp and strengthen follicles, helping reduce hair loss. Some sources even claim regular application speeds growth and partly restores the original color of gray hair. Although not fully proven, onion water is known to increase scalp circulation and support hair health. Its antiseptic effects may also relieve dandruff or scalp eczema.

• Effects on Women's Health and Menstrual Cycles: Does onion water bring on menstruation? Onion water is a common herbal approach among women with irregular periods. Its antioxidants and certain volatile compounds are thought to support hormonal balance and stimulate menstruation . People with delayed periods from polycystic ovary syndrome (PCOS) or hormonal imbalance report that consuming it for two weeks helps start menstrual bleeding. Although not scientifically established, it may be tried as a harmless herbal supplement for menstrual problems. Traditionally, it is also said to relieve period pain.

• Infections and the Respiratory Tract: Onion water is known as a supportive approach, particularly in winter, for protection against flu and colds . Its antiviral and anti-inflammatory effects may shorten upper respiratory infections such as colds or sinusitis. Onion water for cough is another common home remedy. Mixed with honey, it may loosen phlegm and soothe coughing. Its antioxidants may also help chronic cough by improving the body's resistance. Onions are traditionally called a “natural syrup”; juice produced by leaving onion with sugar is a traditional remedy for productive cough in children.

• Bone and Joint Health: Certain minerals and flavonoids in onion water may benefit bone density. Its calcium and vitamin K content in particular is thought to strengthen bones and reduce osteoporosis risk later in life. Anecdotal reports also suggest that its anti-inflammatory effects relieve joint pain. Some users report modest improvements in menopausal bone loss and hot flashes after consuming onion water.

These points illustrate the broad range of potential benefits. In summary, onion water stands out as a natural supplement that strengthens defenses against cellular damage, supports immunity, and may benefit the heart, skin, and hair. Everyone responds differently, however, so its use should be assessed according to individual tolerability .

How Is Onion Water Prepared?

It is easy to prepare at home with just a few ingredients. For an onion water regimen recipe , people usually choose brown-skinned bulb onions ; red or white onions are not recommended for this regimen. The steps are as follows:

1. Prepare the onion: Choose a medium brown-skinned onion and peel it. For more thorough cleaning, you can soak and wash it in vinegar water before peeling. This helps remove pesticide residues.

2. Boil the water: Pour 2 glasses (approximately 500 ml) of chlorine-free water into a small saucepan, preferably drinking water. Bring to a boil over high heat.

3. Boil the onion: When the water boils, cut the prepared onion into 4 pieces and add it. Cover and simmer over medium heat for about 5 minutes. The onion pieces release their compounds into the water.

4. Strain: After 5 minutes, remove from the heat. Strain out the onion with a clean cloth or fine sieve. The light-brown liquid is onion water.

5. Prepare to drink: Allow it to cool slightly. Neither hot nor cold, lukewarm is best. Very hot liquid may irritate the throat, while very cold liquid may reduce the desired effect. Once lukewarm, it can be drunk directly.

6. Consume fresh: Fresh preparation is important. Avoid making more than you will drink at one sitting. Preparing a fresh batch each day better preserves active compounds.

How Long Should an Onion Water Regimen Last? The usual recommendation is one glass in the morning and another in the evening, regularly for 15 days, followed by a break of about 3-6 months. Some repeat this 15-day regimen several times yearly if needed. This is based entirely on traditional experience, however, rather than a scientifically established protocol. If trying it for the first time, taking a break after 15 days and observing your body may be useful.

The strong taste is not easy for everyone. If necessary, sweeten it with honey while lukewarm. Besides softening the flavor, honey provides additional antimicrobial benefits. Alternatively, cooling it and adding a little lemon may improve the taste.

Does Onion Water Help You Lose Weight?

Onion water is a natural approach frequently used by people seeking weight loss. Does it really help? Yes, it may help indirectly. Onion water is low in calories , with only a few per 100 ml, and its nutritional value supports the body during dieting. Drinking it on an empty stomach in the morning is particularly said to speed metabolism and stimulate fat burning.

Its compounds may increase heat production, called thermogenesis , leading to greater calorie expenditure. Its diuretic effect also removes retained fluid and may produce a rapid fall in scale weight. Appetite control is another possible benefit; drinking it on an empty stomach may promote fullness and help reduce food intake during the day.

However, onion water is not a miracle weight-loss remedy on its own. Losing weight primarily requires reducing calorie intake and increasing energy expenditure. Onion water should be considered an addition to healthy eating and exercise. Drinking it in the morning while eating an unbalanced, high-calorie diet all day will not provide the expected benefit. Instead, use it as support alongside balanced eating and regular activity. In this way, its potential fat-burning and fluid-removing effects may help you lose weight faster and more healthily.

Does Onion Water Bring On Menstruation?

Many women with irregular periods seek herbal approaches, and onion water is frequently mentioned. Could onion water stimulate menstruation? Although firm scientific evidence is lacking, there is a strong traditional belief and some positive feedback.

Certain onion flavonoids and antioxidants are thought to regulate the female reproductive system. They are claimed particularly to support ovulation and regulate menstrual cycles . Some women report that 7-10 days of onion water successfully starts a delayed period. Some alternative practitioners also suggest it can shrink uterine polyps or cysts, but no clear study supports this in the medical literature.

Despite scientific uncertainty, use to bring on menstruation is common because moderate amounts have not been observed to cause serious harm. If you wish to try it, one glass morning and evening for 7-15 days while your period is delayed is suggested. Many report that bleeding starts after completing the regimen. Although the mechanism is unclear, hormonal balancing and improved circulation are thought to contribute.

An important point: If pregnancy is possible, do not use an onion water regimen; take a pregnancy test first. If pregnancy explains the delay, using onion water or another menstrual stimulant is inappropriate. Women with serious hormonal disorders or chronic conditions should also consult a doctor beforehand. Remember that onion water may support menstrual regularity but does not treat the underlying cause. Persistent problems require gynecological assessment.

Does Onion Water Promote Hair Growth?

Although the strong smell may initially make application unappealing, onion water has been used for hair health for years. Does it actually promote growth or strengthen hair? Applying it directly to the hair and scalp may offer several benefits:

• Reducing Hair Loss: Sulfur in onion water acts almost like fertilizer for hair roots. Sulfur is needed for hair keratin; when applied to the scalp, it reaches follicles and promotes stronger strands. Some small studies have observed faster hair regrowth in patients with alopecia areata (patchy hair loss). Reduced shedding with regular use is a commonly reported traditional experience.

• Faster Growth and Thicker Hair: Massaging onion water into the scalp increases local circulation. Greater blood flow delivers more nutrients and oxygen to follicles, potentially promoting faster growth and thicker strands. People applying it to the roots several times weekly report faster growth and new fine “baby hairs” within 1-2 months.

• Addressing Scalp Problems: Antibacterial and antifungal properties may help with dandruff, eczema, and fungal scalp infections. Its antiseptic effects may accelerate healing of scalp sores or redness. It may also balance excess sebum and reduce dandruff.

• Effects on Gray Hair: Traditional claims suggest onion water stops graying and darkens gray strands. Although scientific support is weak, theories propose that onion antioxidants and catalase neutralize hydrogen peroxide in follicles and slow graying. Improved overall scalp health may at least produce healthier, more pigmented new hair.

How Do You Make an Onion Water Hair Mask? There are two methods. First, prepare it as described above and allow the onion water to cool before applying it directly to the roots. Alternatively, grate raw onion and squeeze it through cloth to obtain fresh juice, which smells stronger but may be more effective. Spread it over the scalp with cotton or a spray bottle, then massage with fingertips for a few minutes. Leave for at least 30 minutes, preferably 1-2 hours. Shampoo thoroughly and rinse; adding a few drops of lavender oil to shampoo may reduce the smell. Repeat 2-3 times weekly.

Caution: Before a first application, test a small skin area for allergy. Onion water can cause redness and irritation in some people. If severe burning or redness occurs, wash it out immediately. Applied moderately at regular intervals, it may provide natural, economical hair care.

Can Onion Water Be Put in the Ear?

Ear pain, particularly middle ear infection (otitis), is uncomfortable and often requires antibiotics. Traditional home approaches have also been used to relieve pain. Putting onion water in the ear is one such method.

Onion sulfur compounds and anti-inflammatory properties may help when applied to an ear painful from infection. How Is It Applied? Grate a clean bulb onion and extract its juice; raw onion juice is more suitable for this purpose. Bring a few fresh drops to a lukewarm temperature, for example by warming them in a spoon above hot water, without making them too hot. Using a dropper, put 2-3 drops into the painful ear. Lie on that side for a while to let the liquid penetrate. This may be repeated 2 times daily.

As a natural antibacterial , onion may reduce infection-causing bacteria in the ear. Its anti-inflammatory substances may also relieve swelling and pain in the Eustachian tube. Ear pain and signs of inflammation may improve after several applications.

Onion water should, of course, be considered only a supportive approach for mild ear pain . Severe pain, high fever, or ear discharge requires medical attention. Middle ear infection is common in children, and antibiotics are important when indicated. Onion water should not delay medical treatment. If your eardrum is perforated, never put any liquid in the ear, because onion water and other liquids may be harmful.

In summary, onion water for ear pain is an old home remedy that may offer temporary relief. Correct use may reduce inflammation and pain, but medical advice takes priority, particularly for children or serious cases.

Does Onion Water Help Cough?

Onion is among the first remedies that come to mind for natural cough treatment. Can onion water or an onion regimen stop a cough? Partly yes, particularly for a productive cough. Onion's antimicrobial and antioxidant components help clear the airways, strengthen immunity, and speed cough resolution.

Several onion-based methods are used:

• Drinking Onion Water: Drink 2 glasses daily, lukewarm and prepared as described above. If the flavor is too strong, a spoonful of honey sweetens it and adds a soothing effect for the throat. Particularly at bedtime, this mixture may reduce coughing fits and improve sleep.

• Honey-Onion Syrup: Chop one bulb onion and place it in a jar. Add 2-3 tablespoons of honey, mix, close the lid, and leave for several hours. The onion will release juice into the honey. Take this onion-honey syrup in dessert-spoonfuls 3-4 times daily. It may also soothe cough in children over 1 year of age. Onion's antimicrobial activity and honey's soothing effect work together.

• Onion Steam: If cough accompanies postnasal drip and congestion, chop a large onion into a bowl of boiling water. Lean over it with a towel covering your head and inhale the onion steam for 5-10 minutes. Volatile onion oils open the airways, loosen phlegm, and relieve coughing.

Scientifically, onion compounds such as sulfur compounds and flavonoids are known to have anti-inflammatory effects and fight upper respiratory microbes, accelerating recovery. Some studies suggest onion and garlic may shorten colds. Because coughing is often a reflex following viral infection, suppressing the underlying infection matters, and onion water provides support. It may also reduce sensitivity of the cough reflex.

In conclusion, drinking onion water or using a honey-onion regimen for cough is an approach you can safely try, particularly for early or nighttime coughing. If a cough persists beyond 1-2 weeks, worsens, or accompanies high fever or shortness of breath, consult a physician.

Risks and Adverse Effects of Onion Water

Like anything else, excessive or incorrect use may cause adverse effects. A natural product is not necessarily completely harmless. Potential risks and situations requiring caution include:

• Stomach and Digestive Problems: Onion water may irritate the stomach, particularly in sensitive people. Excessive consumption may cause bloating, gas, and acid indigestion . Certain fermentable carbohydrates (FODMAPs) in onions increase intestinal gas and may cause bloating and pain. In people with reflux, onion water may trigger heartburn and other symptoms. People with stomach ulcers or gastritis are therefore advised to try it cautiously or avoid it.

• Low Blood Sugar (Hypoglycemia): Because onion water may lower blood sugar, people with diabetes should consume it cautiously. If you use insulin or tablets, onion water could lower blood sugar excessively and cause hypoglycemia, with sweating, palpitations, dizziness, or even fainting. Discuss its use with your doctor and monitor blood sugar more frequently. Starting with a small amount and observing your response may be safer.

• Blood-Thinning Effects: Onion compounds may somewhat reduce blood clotting. Although generally considered beneficial for the heart, this may pose risks for people with clotting disorders or those taking blood thinners. In patients taking warfarin, heparin, or aspirin, onion water may enhance the medicine's effect and cause unwanted bleeding. People with bleeding disorders such as hemophilia should also avoid it. Foods with potential blood-thinning effects, including onion water, should be stopped at least 1 week before surgery.

• Excessive Fluid Loss (Dehydration): Large amounts may cause excessive fluid loss because of onion water's diuretic properties. Without enough water, dehydration may follow. Drinking liters daily is inappropriate, particularly in hot weather or when fluid intake is already inadequate. Drinking a glass of plain water for each glass of onion water may maintain balance.

• Allergic Skin Reactions: Some people are allergic to onion or onion water. Applied to the skin rather than taken orally, it may cause redness, itching, or rash as allergic contact reactions. Stop facial or acne applications if irritation develops. Oral consumption may also rarely cause itchy skin eruptions (hives).

• Headache: Excessive intake or marked sensitivity has reportedly caused severe headaches . The reason is unclear but may involve blood vessel dilation from active compounds. If unusual headaches develop during use, take a break for several days to see whether they improve.

• Pregnancy and Breastfeeding: Although onions are generally safe in food, concentrated onion water regimens during pregnancy are not recommended. Onion water prolongs bleeding time, and high intake in pregnancy could theoretically increase miscarriage risk. It may also worsen nausea in an already sensitive stomach. Small amounts may not trouble breastfeeding mothers, but the smell can pass into milk and make the baby unsettled. During these periods, consult your doctor before starting herbal regimens.

• Medicine Interactions: Beyond diabetes medicines and blood thinners, onion water may interact with diuretics and blood pressure medicines. A concentrated regimen combined with a diuretic, for example, may cause excessive potassium loss or low blood pressure. People taking regular medicines, particularly for chronic disease, should therefore speak to their doctor before starting.

In view of these effects, consumption requires moderation and attention to the body's response. Although 1-2 glasses daily are usually tolerated, substantially more may cause more harm than benefit. Stop if symptoms such as stomach pain, dizziness, or itching occur, and seek medical attention when necessary. Remember that natural treatments also require informed use.

Onion Water and Cancer: What Does Research Say?

Vegetables such as onion and garlic in the Allium family have long been studied for potential cancer protection. Does onion water help cancer or prevent it? Current knowledge does not justify answering yes, although research highlights several important points:

• Laboratory Findings: Experiments with onion extracts or compounds in cell cultures and animals have produced promising results. A Canadian study found red onion extract most effective among onion varieties at killing colon and breast cancer cells. The extract triggered apoptosis , controlled cell death, and slowed tumor cell proliferation. Another study reported that combined garlic and onion extracts inhibited tumor growth in mice more than either alone. These findings suggest that active onion compounds may act directly against cancer cells.

• Specific Compounds: Certain onion components are of interest in cancer research. For example, organosulfur compounds and flavonoids may suppress cancer cell proliferation pathways. A molecule such as allicin , abundant in garlic and present in smaller amounts in onion, may inhibit enzymes involved in tumor formation. Substances such as S-allyl cysteine and ajoene in onion have also been investigated for anticancer potential. Some studies suggest they can inhibit tumor-feeding blood vessel formation (angiogenesis) and activate immunity against cancer.

• Onion Water Versus Raw Onion: A widely discussed Puerto Rican study found that women consuming raw onion and garlic daily had a 67% lower likelihood of breast cancer than nonconsumers. Researchers notably emphasized that cooking reduced these protective effects . Raw consumption, and possibly raw juice, may therefore preserve beneficial compounds best. Although onion water is usually boiled, raw juice obtained by grating and squeezing may offer an advantage for cancer prevention. Its taste and stomach effects may not be tolerated by everyone, however. There is a balance: gentle boiling reduces some antioxidants but still transfers a substantial proportion into the water.

• Preventive Support, Not Direct Treatment: No human clinical treatment study has been conducted on onion water or onion extract. No oncologist would therefore say that drinking onion water alone can treat cancer.

Frequently Asked Questions

How Often Should Onion Water Be Drunk?

An onion water regimen generally consists of 2 glasses daily, morning and evening, for 15 days followed by several months off. For example, after 15 days, take a 3-6-month break and repeat for another 15 days if needed. Courses rather than continuous use are preferred to avoid adaptation and possible adverse effects. Stop early if discomfort occurs.

Should Onion Water Be Drunk Hot or Cold?

Onion water should be consumed lukewarm , neither boiling hot nor chilled from the refrigerator. Lukewarm liquid is better for the throat and ideal for the intended effects. After boiling, wait until it cools to this temperature.

Should It Be Taken on an Empty or Full Stomach?

Onion water is generally recommended on an empty stomach . Drinking it upon waking and some time before the evening meal facilitates absorption and may increase the intended effects. It is said to stimulate metabolism and fluid removal more on an empty stomach. If your stomach is very sensitive, try a light snack first, although most people tolerate it better without food.

Does Onion Water Cause Weight Gain?

No, onion water does not cause weight gain. Used correctly, it may instead support weight loss. It is very low in calories and contains compounds that promote fat burning. Neglecting your diet will not produce a magical effect, but consumed within a regular, moderate diet, onion water is certainly not a cause of weight gain . Its fluid-removing effect may even lower scale weight.

Does Onion Water Increase the Chance of Pregnancy?

There is a traditional belief that onion water benefits reproductive health , particularly in women seeking pregnancy. Its vitamins and antioxidants are thought to benefit the ovaries. Some women with ovulation difficulties report becoming pregnant after an onion water regimen. Although not scientifically established, some believe it can stimulate ovulation and cleanse the uterus. Because it is thought unlikely to cause harm, people planning pregnancy may try it. They should not expect miracles, however, and should remember that medical assessment and treatment of any underlying problem are what matter most.

Can Onion Water Be Applied to the Face?

Yes, onion water can be used externally for skin care . Its antiseptic and antioxidant effects may help when applied with cotton, particularly for acne. Direct application helps dry pimples through antibacterial activity and cleans pores. Sulfur and vitamin C also support collagen production and may lighten skin spots and reduce wrinkles. Apply fresh juice with cotton, leave for 10-15 minutes, and rinse with lukewarm water. Repeat several times weekly. Test a small area first because irritation can occur. Avoid the eye area, as onion water can sting the eyes.

Which Onion Should Be Used?

The most recommended type is a brown- or yellow-skinned bulb onion, the standard cooking onion found in supermarkets. Some say red or white onions can also be used, but traditional recipes consider brown onion more suitable. Although red onions are rich in antioxidants, brown onions are reputed to be more effective at stimulating menstruation. Choose a medium brown-skinned onion where possible. It should be fresh and firm, not soft or sprouting.

How Can the Smell of Onion Water Be Removed?

Drinking onion water may leave a strong smell on the breath and skin. Chewing parsley afterward can freshen breath and mask the smell; mint leaves or cloves may also help. Brushing teeth and rinsing with salt water freshen the mouth. After skin application, washing and wiping with rosewater may remove odor and soothe the skin. Using the regimen in the evening followed by a shower is another way to minimize smell. Remember that the odor is temporary, while benefits may matter more over time.

Who Should Not Drink Onion Water?

In some situations, drinking it may be inappropriate. People with stomach ulcers or gastritis or active digestive problems should know that onion water may worsen symptoms. People with diabetes and those taking blood-thinning medicines should also be cautious and preferably avoid it, as discussed above. Breastfeeding mothers may avoid it in the early months because it can cause gas in the baby. People allergic to any vegetable or food should also be careful, as onion allergy is possible. If you have a chronic condition or take regular medicines, consult your doctor before starting an onion water regimen.

Conclusion

Used correctly and without excess, onion water is a natural supplement that may offer several health benefits. It is widely used particularly for immune support, faster metabolism, and menstrual regularity. As with any natural approach, individual differences and amounts are very important. 

Although scientific data suggest onions' rich antioxidants may protect against many diseases, onion water should not be seen as a miracle on its own . It is best regarded as part of healthy living and a supplement to balanced nutrition.

If you decide to try an onion water regimen, use the information here as a guide, observe your body's response, and consult a professional when necessary. Remember that protecting health requires sustainable, scientifically supported steps. Natural wonders such as onions are supportive tools along this path.