OPC stands for oligomeric proanthocyanidins, a group of powerful antioxidant compounds. They are commonly found in grape seed extract, which in lab and animal studies has been shown to make blood vessels more elastic and less likely to leak fluids, thus decreasing the leg swelling often associated with varicose veins. OPC-3, a product containing these compounds, is being widely promoted on the Internet as a treatment for diseases associated with free radical damage. However, I have seen no studies suggesting that OPC is an effective treatment for allergies or asthma.
(Grape seed extract is commonly prescribed in France for varicose veins and other vascular problems. I generally recommend it along with horse-chestnut seed extract [HCSE], a more extensively studied treatment for these conditions.)
Asthma is a chronic inflammatory condition characterized by repeated episodes of airway obstruction and associated with an exaggerated airway response to a variety of inhaled stimuli. Although the cause is unknown, such factors as allergies, increased stress, respiratory infections, and exercise can worsen asthma. It can also occur without any obvious triggers.
Allergies are due to "misplaced immunity" against something that really is not a threat to health. Allergic responses are also learned responses that can be unlearned. The goal of treatment should be to convince the immune system that it can coexist peacefully with the substances it is reacting to. In young children, it is important to try to limit exposure to potential irritants of the immune system.
Instead of trying products like OPC-3, my principal recommendation for patients with asthma and allergies (or both) would be to follow an anti-inflammatory diet. Increase organic fruits and vegetables, and stay hydrated with lots of water. Avoid processed foods, partially hydrogenated oils, white sugar, and flour. I also recommend using standard medical treatment selectively and trying to avoid suppressive medications (such as oral steroids) as much as possible. Use mind-body medicine such as guided imagery or clinical hypnosis and experiment with homeopathy as well since children respond favorably to this form of treatment.
Andrew Weil, M.D.