In yoga, a Pranayam is a breathing technique. An especially powerful breath for enhancing immune function is Sitali, the cooling breath.
Stick your tongue slightly out of your mouth and curl the sides upward, like forming a tube or trough. Slowly and steadily inhale through the curled tongue, hold for a few seconds, and exhale through the nostrils (keeping the tongue out the whole time). Continue this breath for five minutes.
You may experience a bitter taste on your tongue. This usually indicates that your body is toxic and, with practice, the taste will go away.
Sitali Pranayam is useful for cooling down a fever, calming the mind by removing tension and anxiety, healing the digestive system and for rejuvenating the body. It is said in mystical terms that this breath will make the heavens serve you.
Click here for more meditations that use Sitali Pranayam.