I have asthma very bad, and every time I get sick I can't smell for a long period of time. Sometimes this happens when I'm not sick. Can you tell me why?

S.

Smell and taste are chemical senses: Your nose and tongue are able to detect very dilute concentrations of chemicals and are able to differentiate among hundreds of different ones. The specialized cells, or "receptors," that do this detective work are (in the case of smell) located at the very roof of the nasal cavity. Put your fingertip on the bridge of your nose, right between your eyes. Imagine an area about one inch deep beyond your fingertip. That's where all the action is.

You can smell chemicals only if they are airborne. Yes, you can smell liquids, but that's because a small portion of the liquid is becoming a gas at any given instant. When we inhale through our noses, a portion of the inhaled air circulates to the roof of the nose. Any chemicals present in this air will dissolve into the mucus that coats the receptors for smell. The dissolved chemicals trigger the appropriate receptors, and your brain interprets this information appropriately.

Anything that blocks this chain of events will result in anosmia (loss of the sense of smell). If your nose is too congested, no air will circulate to the roof of the nasal cavity. If your nose is excessively dry and there is an inadequate mucus layer covering the receptors, then the gaseous chemicals will have difficulty dissolving into the mucus.

Many drugs can affect the degree of nasal congestion or the consistency of nasal mucus, and it is possible that one or more of the drugs you take for asthma are causing anosmia in this fashion. In addition, many drugs act directly upon the receptors to cause anosmia. Your doctor may have to sit down with a list of your medications and the PDR (the Physician's Desk Reference, which has detailed information on all prescription drugs) to figure this one out.

This assumes that your anosmia is a consequence of your asthma treatment. There is another possibility, however. Folks with chronic infection of the nose and sinuses who also have asthma often notice that the infection and the asthma seem interrelated. The infection may result in nasal mucus (containing bacteria, pus and inflammatory chemicals) making its way down to the lungs and provoking an attack of asthma. An acute worsening of the infection will also be associated with nasal inflammation, which causes decreased air flow through the nasal cavity -- which in turn causes anosmia. Thus, the same infection could be causing both your asthma and your anosmia.

Discuss this problem with your doctor. With appropriate questioning and examination, he or she should be able to differentiate among these possibilities. Your treatment may involve changing the drugs used in the treatment of your asthma. Alternatively, you may need treatment for rhinosinusitis. This could involve antibiotics, other drugs to reduce nasal inflammation or treat nasal allergies, and (if all else fails) surgery to improve sinus drainage.