Overview

Onion (Allium cepa) is a plant that is grown worldwide. The onion bulb is commonly eaten as food. Onion bulb and extract are also used to make medicine.

Onion contains chemicals that seem to reduce swelling and lung tightness related to asthma. It also contains chemicals that seem to reduce cholesterol and lower blood sugar.

People use onion to prevent scarring. It is also used for obesity, hair loss, asthma, insomnia, high blood pressure. warts, and many other conditions, but there is no good scientific evidence to support these uses.

Uses & Effectiveness

Possibly Effective for

  • Scarring. Applying a gel containing onion extract to the skin, alone or with other ingredients, for at least 10 weeks seems to improve the appearance of scars. But it's not clear what combination of ingredients or dose works best.

Possibly Ineffective for

  • Obesity. Eating onion or taking onion extract by mouth doesn't reduce body weight in people who are overweight or obese.

There is interest in using onion for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.

Side Effects

When taken by mouth: Onion is commonly consumed in foods. Onion extract is possibly safe when used as medicine in doses up to 900 mg daily for up to 12 weeks. Side effects might include stomach pain and heartburn.

When applied to the skin: Onion extract is likely safe. Side effects might include skin irritation or eczema.

Special Precautions and Warnings

When taken by mouth: Onion is commonly consumed in foods. Onion extract is possibly safe when used as medicine in doses up to 900 mg daily for up to 12 weeks. Side effects might include stomach pain and heartburn.

When applied to the skin: Onion extract is likely safe. Side effects might include skin irritation or eczema.

Pregnancy and breast-feeding: Onion is commonly consumed in foods. But there isn't enough reliable information to know if onion is safe to use in larger amounts as medicine when pregnant or breast-feeding. Stay on the safe side and stick to food amounts.

Cross-allergens: People with allergies to mugwort and celery might also be allergic to onion.

Surgery to place a pouch near the anus (ileal pouch-anal anastomosis): People that have had surgery to place a pouch near the anus might find that onion increases feelings of gas. Don't eat large amounts of onion if you have had this surgery.

Indigestion: Onion might increase indigestion symptoms.

Surgery: Onion might slow blood clotting and lower blood sugar. This might increase the risk for bleeding or interfere with blood sugar control during and after surgical procedures. Stop using onion as a medicine at least 2 weeks before a scheduled surgery.

Interactions

    Moderate Interaction

    Be cautious with this combination

  • Medications changed by the liver (Cytochrome P450 2E1 (CYP2E1) substrates) interacts with Onion

    Some medications are changed and broken down by the liver. Onion might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

  • Aspirin interacts with Onion

    Some people are allergic to onions. Aspirin might increase your sensitivity to onions if you are allergic to onions. This has only been reported in one person. But to be on the safe side, if you are allergic to onions do not take aspirin and eat onions.

  • Medications for diabetes (Antidiabetes drugs) interacts with Onion

    Onion might lower blood sugar levels. Taking onion along with diabetes medications might cause blood sugar to drop too low. Monitor your blood sugar closely.

  • Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs) interacts with Onion

    Onion might slow blood clotting. Taking onion along with medications that also slow blood clotting might increase the risk of bruising and bleeding.

Dosing

Onion is commonly consumed in foods. As medicine, there isn't enough reliable information to know what an appropriate dose of onion might be. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult a healthcare professional before using.
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CONDITIONS OF USE AND IMPORTANT INFORMATION: This information is meant to supplement, not replace advice from your doctor or healthcare provider and is not meant to cover all possible uses, precautions, interactions or adverse effects. This information may not fit your specific health circumstances. Never delay or disregard seeking professional medical advice from your doctor or other qualified health care provider because of something you have read on WebMD. You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you.

This copyrighted material is licensed from Therapeutic Research Center, LLC. Information from this source is evidence-based and objective, and without commercial influence. For professional medical information on natural medicines, see Natural Medicines Comprehensive Database Professional Version.
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