TYPES OF ALLERGIES

    Introduction

Food allergy is well recognized in clinical medicine as a cause of acute attacks of asthma, angioedema and urticaria, and as a contributing factor in some cases of eczema and rhinitis. These types of allergic reactions are considered to be mediated by IgE antibodies, and usually can be diagnosed by medical history and skin-prick or IgE-radioallergosorbent (RAST) tests.

Another type of food reaction, often referred to as "hidden" or "masked" food allergy, has been the subject of controversy for many years. Some practitioners have observed that hidden food allergies are a common cause of (or triggering factor for) a wide range of physical and emotional disorders. According to one estimate, as many as 60 percent of the population suffers from undetected food allergies.¹ A wide range of symptoms and disorders are reported to have a significant allergy component. This diagram shows conditions which frequently have allergic components:

• Aphthous ulcers
• Arthritis
• Asthma
• Attention deficit-hyperactivity disorder (ADHD)
• Eczema
• Enuresis
• Epilepsy
• Fatigue
• Gallbladder disease
• Inflammatory bowel disease
• Irritable bowel syndrome
• Migraines
• Other recurrent infections
• Otitis media
• Psoriasis
• Rhinitis

[Webmaster's note: I feel it is fair to include Chronic prostatitis/CPPS in this list, based on the anecdotal experience of many men]

On the other hand, many conventional physicians doubt hidden food allergy is a common problem, and some even deny altogether its existence as a clinical entity.

Skeptics emphasize the fact that many of the conditions said to be related to allergy fluctuate in severity and have a significant psychological component. Consequently, it may be difficult to distinguish between a true food reaction and a conditioned (psychogenic) response or a spontaneous exacerbation of symptoms. It also has been pointed out that food-induced symptoms should not be called allergies unless an immune-mediated mechanism can be demonstrated. While it is true many food reactions would be more appropriately labeled food intolerance, the term "allergy" will be used in this article in reference to adverse reactions to foods.

Proponents of the food allergy-disease connection argue that hidden food allergies are often overlooked because they are difficult to identify. Unlike the more obvious immediate-hypersensitivity reaction that can trigger acute asthma or anaphylaxis, a hidden food reaction frequently can be delayed by many hours or even several days.

Identifying a cause-effect relationship between ingestion of specific foods and development of symptoms is said to be further complicated by the tendency of people to become addicted to the foods to which they are allergic. This so-called "allergy-addiction syndrome" has been observed by numerous clinicians² and appears to be consistent with Selye's description of the "general adaptation" response to stress.^3,4 Thus, patients often experience short-term relief after ingesting foods which are later demonstrated to be the cause of their chronic symptoms. This paradoxical response can render medical histories and diet diaries virtually useless for detecting hidden allergies.

Hidden food allergies can usually be "unmasked" by means of an elimination diet.⁵ After a patient has been on a hypoallergenic diet for a period of time (typically one to three weeks), chronic symptoms disappear or improve and the body reverts from a state of allergy-addiction (corresponding to Selye's adaptation stage) to one of increased alertness and sensitivity (corresponding to Selye's alarm stage). In this hypersensitive state, ingestion of an offending food results in a rapid and exaggerated reaction, allowing the patient to identify previously unsuspected allergens. Here is a list of foods most commonly associated with food allergies or intolerances:

Ideally, studies of hidden food allergy should be conducted using double-blind, placebo-controlled food challenges, in order to rule out placebo responses and spontaneous fluctuations in symptom severity. Some of the research reviewed in this article has used a double-blind design; and most of these studies have confirmed the importance of food allergy in the etiology of certain chronic conditions. Most of the other studies on food allergy have lacked placebo controls. Nevertheless, the results of these studies have frequently been impressive, especially when compared with results of conventional therapy. Following is a review of selected studies on the relationship between food allergy and certain common medical conditions.

Migraine

Food allergy has been mentioned as a cause of migraine as early as 1930. In a study of 55 migraine patients, avoidance of allergenic foods, combined with general supportive care, resulted in complete or near-complete freedom from symptoms in 29 patients (52.7%) and partial improvement in an additional 21 (38.2%).⁶ In a 1935 study, 66.3 percent of 127 migraine patients experienced partial or complete relief of symptoms after following an elimination diet.⁷ Heymann reported in 1952 that food reactions were the cause of migraine in 15 of 20 patients.⁸ Speer also found that foods (mainly milk, chocolate, cola, and corn) were common triggers for migraine.⁹

Egger et al placed 88 children suffering severe, frequent migraines on an oligoantigenic diet consisting typically of one meat (lamb or chicken), one carbohydrate (rice or potato), one fruit (banana or apple), one vegetable (Brassica), water, and vitamin and calcium supplements for 3-4 weeks.¹⁰ Patients who did not improve were offered a second oligoantigenic diet, with no foods in common with the first diet. Seventy-eight children recovered completely on the first or second oligoantigenic diet, and four improved markedly (total recovery rate, 93%). Of the 82 patients who improved, 74 developed symptoms after one or more individual food challenges. Forty of these 74 patients participated in double-blind, placebo-controlled food challenges, which confirmed the etiologic role of food allergy. Most patients reacted to several foods. Fifty-five different foods provoked symptoms, the most common of which were (number of patients in parentheses): cow's milk (27), egg (24), chocolate (22), orange (21), and wheat (21).

Grant studied 60 patients with a history of frequent and recurrent migraines.¹¹ The mean duration of illness was 18 years for women and 22 years for men. Each patient consumed an oligoantigenic diet for five days, consisting only of two low risk foods (usually lamb and pears) and drank only bottled spring water. Migraines disappeared by the fifth day in most cases, after which foods were tested individually. The mean number of symptom-provoking foods was ten per patient (range, 1-30). The foods most frequently causing symptoms and/or pulse changes (a presumed indicator of allergy) were wheat (78%), orange (65%), egg (45%), tea and coffee (40% each), chocolate and milk (37% each), beef (35%), corn, cane sugar and yeast (33% each), mushrooms (30%), and peas (28%). When the offending foods were avoided, all patients improved. The number of headaches in the group fell from 402 to 6 per month, and 85 percent of the patients became headache-free.

Monro et al provided evidence that at least some food-induced migraines are true allergic reactions (as opposed to being mediated by vasoactive compounds).¹¹ Nine patients with food-induced migraines were treated in double-blind fashion with sodium cromoglycate (a drug which blocks mast-cell degranulation and allergic reactions) or a placebo, along with foods previously identified as symptom provokers. Sodium cromoglycate was significantly more effective than placebo in preventing the development of migraines. Challenge with offending foods resulted in the appearance of IgE-containing immune complexes; this was prevented by pretreatment with sodium cromoglycate, but not placebo.

Arthritis

Food allergy was mentioned by Kaufman in 1953 as a causative factor in some cases of arthritis.¹² O'Banion reported three patients with rheumatoid arthritis in whom removal of allergenic foods from the diet was followed by complete elimination of arthritis pain.¹³ Ratner et al, reported the case of a 14-year-old female with a six-year history of juvenile rheumatoid arthritis who recovered after