Do onion and garlic really treat a cold?
There is no strong evidence to recommend onion or garlic as a cold treatment or a substitute for appropriate care. They can be foods if tolerated, but garlic supplements have risks, including increased bleeding and medicine interactions.
Details
Food is not a proven treatment
Finding biologically active compounds in garlic does not show that eating it or taking supplements eliminates a cold virus. Clinical evidence is limited. Claims that a particular amount of onion or garlic shortens illness or reliably boosts immunity are not established.
Avoid harmful applications
Do not apply raw garlic to skin or place it inside the nose; irritation and burns can occur. Supplements may cause digestive symptoms or allergy and need particular caution with blood thinners or before surgery. Food quantities and concentrated products have different safety considerations.
Choose suitable symptom care
Rest, appropriate fluids and symptom relief matched to age and health are more useful priorities. Do not delay assessment for breathlessness or marked deterioration while trying a home remedy. Ask a pharmacist about product ingredients, especially for children or during pregnancy.
Related reading: Is vaping safe, and is it less harmful than smoking cigarettes?.