How do garlic and onions kill flu and cold viruses?

Garlic and onions complement each other in more ways than one. These two kitchen staples are so frequently used together that many recipes would not be the same without their joined flavors. Their immune-enhancing effects also make garlic and onions a potentially formidable force against common cold and flu viruses.

Use garlic and onions liberally to avoid catching colds and flu, says author Jordan Rubin in “The Great Physician’s RX for Colds and Flu.” Garlic improves the activity of natural killer cells, a type of immune cell that is specifically designed for cold and flu viruses and cancer cells. Garlic and onions contain compounds that are similar ingredients in over-the-counter cold and flu remedies. These compounds have the ability to dry out congested nasal passages and prevent mucous accumulation. Add horseradish, a plant with similar medicinal qualities to garlic and onions, for a triple threat to any cold or flu virus that comes your way.

Make a soup with six onions, an entire bulb of garlic, about an inch of grated fresh ginger and cayenne pepper to chase away colds and flu, advises health journalist Hazel Courteney, author of the book “500 Health Tips - An A-A of Alternative Health Hints to Help More Than 200 conditions.” Garlic and onions bring antiseptic qualities and cayenne pepper boosts the effectiveness of the other herbs.