By Dr. Mark Cullen
One of the most vexing problems in all allergy is the patient who discovers that certain common smells–sometimes from “chemicals” but often from totally natural things like flowers—make them feel sick. Symptoms can range from typical asthma symptoms, like wheeze, cough or shortness of breath, to strictly upper respiratory symptoms such as difficulty speaking or a feeling the throat is closing, all the way to systemic symptoms like dizziness or confusion or palpitations. To the victim it can be pretty scary, especially when almost everyone’s immediate reaction is to assume that the thing that is causing the smell must be somehow “poison”, possibly even causing something far worse but unknown.
To complicate matters, physicians—even some well-trained allergists—either neglect to ask about smells, or, worse, treat the relationship between the smells and symptoms as unimportant or unhelpful. Many an asthmatic has been told to get a mattress cover to control dust-mites or other allergens, but few have been told to buy fragrance-free household products! However, this is only part of the problem. You may eventually get around to ridding your home of the offending chemicals, but how do you cope with trips to the department store, or getting stuck on the subway next to someone wearing a certain perfume?
The science of the how smells cause physiologic effects is less than fully developed, but no one should be surprised how potent smells can be; after all, the sense of smell evolved to drive critical life functions such as mating or to protect us from approaching predators. Because these triggers were so important, the reactions evolved to match—whether for arousal for mating or flight-or-fight, those hormone levels shoot up.
So why was the scientific world so skeptical 40 years ago when the first studies proved that in some asthma patients, a whiff of a strong smell – even when the air to the nose was blocked from going into the lungs completely—led to immediate wheeze and dramatic decline in airflow? Even 40 years later there is debate about how often this happens, but in many asthma clinics where the question is asked, this experience is far from rare. And while such patients cannot completely avoid some situations in which they will encounter the smells that trigger wheeze or bronchoconstriction, all can be trained to make the modest life adjustments that will minimize unnecessary exposure.
People who feel that certain smells cause them “throat closure” or difficulty speaking are even harder to manage, in part because often the instinct of both doctor and patient is to assume this is asthma. But if the doctor takes the time and trouble to get the full history and then do a test of how the airways are reacting, such as a methacholine challenge test, it becomes clear that the “action” is in the throat, not the lower airways themselves, which is where asthma “happens.”
Amazingly, although surveys of respiratory symptoms in the population show that smell sensitivity is a common problem, there is neither a simple diagnostic protocol for this, nor—more unfortunate still—a proven remedy that works for most who suffer this kind of reaction. The elusive diagnostic protocol is understandable. How do you test for smells when the concentrations are so low? The specific components of randomly encountered airborne fragrance can’t be isolated and injected under the skin the way, say, dust mite allergens can.
But physicians can do these things: 1) advise patients to keep track of situations and environments where smells regularly cause problems 2) help develop strategies to minimize unnecessary exposure (be nice when you tell the man in the adjoining cubicle that his cologne makes you sneeze, or when you tell your child’s teacher about her soap). 3) avoid “over-prescribing” potent-but-effective asthma medications (once asthma has been ruled out by the right tests) such as inhaled steroids, which don’t have a proved value for smell triggered symptoms. Other things may work for some patients, such as capsacian gargles, but none is yet proved and in my experience only a portion of patients demonstrate a clear-cut positive response.
Finally, there’s the patient whose symptoms extend far beyond the throat and chest. Usually these patients ending up having something called multiple chemical sensitivity, or MCS. The diagnosis and management of that are the subject for another day, but it is important for both the patient and doctor to recognize that this constellation falls beyond the normal remedies used for better-understood allergies. When that is the case, allergy remedies not only won’t help (unless there are also common allergies) but may make control of a difficult clinical problem even worse.
Dr. Cullen is Chief of the Division of General Internal Medicine, Stanford University. Previously he was Professor of Medicine and Public Health and Director of the Occupational and Environmental Medicine Program (OEM) at Yale University School of Medicine.