The outer skins of onions provide an exceptionally rich source of plant compounds called flavonoids, especially the powerful antioxidant and anti-inflammatory compound, quercetin.
Quercetin is well known for its powerful ability for lowering LDL cholesterol and blood pressure, fighting allergies, reducing inflammation, enhancing muscle growth and function, treating depression, some forms of cancer, and other conditions.
Plants are the master chemists. Because plants can’t move around, they have to manufacture what they need, not merely to grow, but to defend, protect, and heal themselves. It makes sense that the compounds plants produce in response to stress would help a human under similar circumstances.
Plants concentrate many of these protective compounds in the outer coverings such as the skins and peels of various roots and fruits. This is the point where most environmental assaults would likely occur. This means the skin is not only highly nutritious but, it is bitter and tough. This is a byproduct of the plant’s defense mechanism.
To use onion skins for culinary purposes you can add them to fermented foods like sauerkraut and Kim Chee. This concentrates the Quercetin and hides the bitter taste while tenderizing the tough skin. For external use, you can make an onion-skin infusion and use the tea as a softening and smoothing hair rinse. This infusion can also be used as a soothing wash for the itch of scabies and other skin disorders.