Though it has never been directly proven that yoga can prevent or treat colds, yoga has been shown in some studies to improve the functioning of the immune system, which may be due in part to its demonstrated ability to reduce levels of the stress hormone cortisol. Short-term elevations in cortisol levels actually improve immunity, but persistently high levels ultimately undermine it and may set the stage for colds and other health problems.
Beyond yoga's role in preventing colds, however, a number of yogic practices can help reduce the symptoms and possibly shorten the duration of the illness. Here are a few suggestions.
Use a neti pot. A neti pot can be used to cleanse the nasal passages with warm salt water, which removes excess mucus and improves breathing. It may also help clear the small openings to the sinuses, potentially preventing the development of a secondary bacterial infection. Fill the neti pot with warm salt water (eight ounces of warm water mixed with a quarter teaspoon of noniodized salt) and place the spout into your right nostril. Tip your head to the left to allow the fluid to flow to the back of your throat, around the sinus area, and out the other nostril. Repeat on the other side. If you suffer from sinus pressure, add extra salt to the water to help draw more mucus out; if you have high blood pressure, congestive heart failure, or any other salt-sensitive condition, skip the salt.
Chant. A Swedish study showed that humming is extremely effective in opening the sinus passages. Chanting "om" is a good choice, as the "mmm" sound resonates strongly in the head. Try holding the chant longer than usual and tune in to the vibrations in your nose and upper palate. Though they haven't been studied scientifically, chants that include an "ahh" sound, which tends to resonate in the chest, might be useful in freeing up mucus there.
Practice more restorative postures. Supported chest openers like Supta Baddha Konasana (Reclining Bound Angle Pose) and supported Setu Bandha Sarvangasana (Bridge Pose) can facilitate deep, restorative breathing. If you have chest congestion, however, they can induce coughing. In that case, try a supported forward bend like Balasana (Child's Pose) over a bolster or supported Upavistha Konasana (Wide-Angle Seated Forward Bend), in which you sit cross-legged and rest your forehead on folded arms on the seat of a chair. Vipariti Karani (Legs-up-the-Wall Pose) and Salamba Sarvangasana (Supported Shoulderstand) are both also ideal for low energy.