CHAPTER 1
The Place of Allergy in Clinical Medicine
The importance of allergy as a vital element in clinical medicine has become strongly established only in recent years. The burgeoning recognition of allergy within the past decade has been nothing short of remarkable. Not too long ago, much of the medical community and a large segment of the lay public considered allergy a questionable condition at best. The opinion “It’s all in their heads” was often expressed when the diagnosis of allergy was suggested. Without any real knowledge of the mechanism involved, and faced with the immense diversity of allergy manifestations, the fact that a physician could express such an opinion was not surprising. All this has changed, however. Now, an informed clinician must consider allergy as possibly playing a significant role, either independently or in combination with another medical problem, in the condition of almost any patient presenting for diagnosis. Failure to diagnose and treat the allergic element may easily result in less than optimal results.
Indeed, the pendulum may have swung too far in some regards. The public, once prone to scoff at all but a few manifestations of allergy, has now embraced the condition as a likely cause for almost any undesirable condition. Foods that a patient dislikes are often represented as foods to which the patient is allergic. Unpleasant working conditions may be reported as places harboring substances to which the worker is allergic. Poor performance in school may be blamed on allergies. Whereas formerly clinicians were often reluctant to make a diagnosis of allergy, they may now frequently find it necessary to modify a patient’s conviction that some form of allergy is at the root of all present problems.
The lay press, attracted to self-diagnosis, has frequently encouraged this image of allergy. A condition with multiple manifestations, often going unsuspected, makes for good reading. A conscientious physician, aware of the prevalence of allergy, must become at least reasonably knowledgeable as to the true extent of the problem and proper approaches to diagnosis and care.
PREVALENCE OF ALLERGY
To address properly the need for becoming involved in treating allergy, the physician must ask certain critical questions: How important is allergy to a practicing clinician? Is it truly widespread enough and debilitating enough to effect the practice? Becoming active in allergy care might entail a considerable investment in time and equipment. A busy clinician needs to know whether such an investment would be justified, regarding both expense and effect on providing improved patient care.
The exact incidence of allergy remains unclear. A fact sheet from the National Institute of Allergy and Infectious Diseases indicates that each year, more than 50 million Americans suffer from allergic diseases, with allergies constituting the sixth leading cause of chronic disease in the United States, resulting in a health care expenditure of $18 billion annually. The prevalence (or at least the diagnosis) of allergic rhinitis in the United States has increased over the past two decades, and an estimated 16% of the general population is believed to suffer from some form of allergy.1
Most studies of allergy incidence consider only inhalant allergy patients. Patients hypersensitive to foods may well constitute an even larger group. No estimate of the number of victims of food allergy has ever been made, in part at least because there is as yet no uniformly accepted definition of food “allergy” as opposed to food “hypersensitivity” or simply “adverse reactions to food.”2 This will be the subject of further discussion in Chapter 13. It is evident, however, that inclusion of this body of patients would significantly increase the total percentage of the population affected by allergy.
Although generally not life threatening, from an economic point of view allergy is not a minor problem. Based on figures reported in 1980, allergic rhinitis then produced two million days of absence from schools annually, plus 3.5 million lost workdays, accounting for $154 million annually in lost wages.3 These figures are undoubtedly higher today, with increased costs and more recognition of allergy as a problem. Realistically, no primary care physician, or indeed any clinician at any level, can afford to ignore the extent of allergy in the population or the degree to which it can effect the success of a practice.
Current estimates are that allergy in one form or another effects some 30% or more of the general population. Otolaryngologists may expect ~50% of the patients encountered in their practices to have allergy as a major or at least a contributing cause of the presenting problem. Because the ear, nose, and throat area accounts for a large percentage of complaints in a family practice, and an even larger segment of a pediatric practice, an understanding of common findings that are frequently allergy related should also be of major benefit in these specialties. As a practical matter, primary care physicians should be prepared to identify patients with allergy.
Bearing this in mind, it is reasonable to ask why the presence of allergy is so often overlooked by the clinician. Allergy in many cases may be a rather subtle condition. Its failure to appear in the forefront of diagnostic considerations is not so much a consequence of its absence in the patient (as its prevalence has demonstrated) as of its tendency to appear in forms other than those most widely recognized by the public, and frequently by the unsuspecting physician. Allergy may not be a presenting complaint. Often, unless an allergy has been diagnosed in the past, or the specific presenting complaint is obviously allergic in nature, as with hay fever or violent food allergy, patients may be unaware of an allergic contribution to their condition. In previous generations, allergy was rarely identified unless it was of the classic “hay fever” type, with sneezing, running nose, conjunctivitis, and all the associated problems of itching and irritation. It was not unusual for such euphemisms as “catarrh,” “sinus,” or simply “postnasal drip” to be reported, and even then, sometimes only in response to specific inquiry. In many cases, because the patient and frequently other family members had the condition throughout most of life, the symptoms were considered a normal, or at least not an unusual, condition. Unless the clinician carried a high level of suspicion and followed up the physical examination with critical questions, the presence of allergy was easily missed.
To make the diagnosis, the clinician must be alert for allergy. The manifestations are multiple but frequently not obvious unless specifically sought. Allergy has been called “the great masquerader” because of its ability to mimic an immense variety of other conditions.
Some examples of commonly overlooked or missed diagnoses of allergy may illustrate the way in which allergy may produce or contribute to familiar problems. Consider the case of a child with repeated episodes of otitis media from infancy. If the problem starts before the age of 1 year, in roughly 80% of cases the child will be found to be allergic. (In most cases, when this appears in infancy, the culprit is food. It can be distressing to find that simple dietary control might have saved repeated myringotomies with tubes, and the attendant risks.) The adult who complains of repeated respiratory infections every month or so, especially without fever, merits an allergy evaluation. Many cases of migraine-type headache are actually allergic in origin. A wide variety of gastrointestinal complaints may actually be food hypersensitivities. In short, almost any medical condition may be imitated by allergy. This does not imply that allergy is the underlying or a contributory problem in all such cases, but only that the possibility warrants consideration, especially if the findings are not exactly those expected for the initial presumptive diagnosis, and even more so if the patient has a personal or family history of other forms of allergy.
Although inhalant allergy confines its symptoms for the most part to the respiratory system, even this is not an absolute limitation. As more information becomes available, the presence of concomitant reactions between inhalants and food becomes more evident, blurring the distinction between inhalant and food triggers. In the case of food sensitivity, almost any organ or organ system may become the target of an adverse reaction. Whereas the pathophysiology of hypersensitivity reactions may be quite similar in a wide variety of responses, the signs and symptoms depend on the target organ, and hence may mimic those of an almost unlimited range of complaints. This seriously compounds the difficulty of diagnosis. It is not unreasonable to state that anything from a headache to halitosis to itching ears may be the result of allergy. This does not mean that all or almost all medical problems are really allergic in nature, but only that when other diagnostic approaches do not provide the expected results, it may be reasonable at least to consider the possibility of an allergic entity.
REFERENCES
1. http://www.niaid.nih.gov/factsheets/allergystat.htm. Last accessed March 17, 2004.
2. King HC. Exploring the maze of adverse reactions to foods. Ear Nose Throat J 1994;73:237–241.
3. U.S. Department of Health and Human Services. Asthma and Allergies: An Optimistic Future. Publication No. 80–388. Bethesda, MD: National Institutes of Health; 1980.
< div class='tao-gold-member'>
