Many asthma sufferers wage a constant battle with low-level congestion. Don't use essential oils during an asthma attack, but between attacks try a chest rub of German chamomile, frankincense or lavender. The chamazulene in chamomile releases cortisone from the adrenals. During an asthma attack, give a bath or treat the feet with these oils. (Hyssop can also be used, but be careful to only use var. decumbens.)

Ninety percent of respiratory ailments are caused by viruses. Oils of thyme, rosemary, peppermint, ravensare, tea tree, eucalyptus, bergamot, black pepper, melissa and hyssop inhibit most flu viruses. Lemon and eucalyptus oils are effective against bacteria that cause staph, strep and pneumonia infections. A 2-percent dilution makes an effective antiseptic gargle or vapor steam.

Steam treatment carries essential oils directly to sinuses and lungs, and provides warm, moist air to help open nasal and bronchial passages. To do a steam, boil a pan of water, turn off the heat, cool 1 minute, add 3-6 drops of essential oils to the water, and use a towel to corral the steam around your head as you breathe deeply. Essential oils can also be used in many humidifiers, or as an ingredient in steamy hot bath water.

If steaming is impractical-at the office, say, or while traveling-inhale a tissue scented with the oils, or use a natural-products nasal inhaler. These are sold in natural food stores, or you can make your own:

Homemade Nasal Inhaler
2 drops eucalyptus
2 drops rosemary
1 drop peppermint
1 tablespoon rock salt

Place a few pieces of rock salt in a vial and add the oils. The salt will quickly absorb the oil. Inhale.

An aromatic diffuser-a glass piece (often hand-blown) connected to a small electrical compressor- disinfects the atmosphere by releasing droplets of essential oil as a cool, fine mist. One advantage to using a diffuser is that the essential oil vapor can be directed into the nose, throat or even ear passages. It can be turned on in a sickroom for 10 to 15 minutes every hour to clear airborne bacteria.

Do not use thick oils such as vetiver, sandalwood, vanilla, myrrh and benzoin in a diffuser unless they are diluted with a thin oil-such as the citruses, eucalyptus or rosemary-or mixed with alcohol. If oils sit too long in a diffuser, they oxidize and thicken. Also, expressed citrus oils often contain sediment that may clog a diffuser. To clean or unclog it, soak the glass unit in alcohol and unplug the opening with a pin or toothpick. Rinse and air dry.

Diluted essential oils can also be used as a throat spray through "nebulization." A nebulizer sprayer, with its long spout that reaches to the back of the throat, used to be a standard item in the home medicine cabinet. A perfume atomizer or spray bottle will work just as well.

If you don't have a diffuser, simply combine water and essential oils in a spray bottle. Studies show that a two-percent dilution of eucalyptus oil kills 70 percent of airborne staph bacteria.