Food allergies: establishment of diagnosis

[Guest guest]

Food allergies: establishment of diagnosis by Barker, Townsend Letter

for Doctors and Patients > Jan, 2004

Allergies, it seems, are everywhere. And does it not seem like more and more

of the people you know are developing some type of allergic symptoms that

they did not have before? A highly complex phenomenon, allergies and their

increased incidence are a puzzling problem. With 50 million Americans

suffering from some type of allergy on a yearly basis, allergy is ranked as the

6th leading cause of chronic disease today, at a cost of $18 billion dollars per

year. (1) Two recent estimates of allergy prevalence in the US were 9% and

16%, (2) and prevalence for the two most common presentations of allergy,

atopic dermatitis and allergic rhinitis, have been increasing since the mid to

late 1980's. (3), (4)

Unfortunately, the aforementioned statistics reflect only allergies that were

clinically diagnosed--established allergic conditions. They do not speak to the

multitudes of allergies that may be manifested by the foods we eat, a clinical

condition that is becoming increasingly well recognized. Not including Type 1

immediate-onset food allergies (which are often life-threatening, requiring the

use of emergency measures), food allergies have been attributed to

numerous conditions, ranging from enuresis (bedwetting) to earaches to

migraine headaches. These allergies are attributable to Type 3 allergic

reactions in which allergens cause an increase in the amount of inflammatory

mediators released by the immune system in the body; symptoms can

become physically manifested up to 72 hours later. The occurrence or

presentation of food allergies is not new, having been documented in the

scientific literature in the 1920's. (5), (6)

What is to explain this increase in allergies over the last few years? A leading

theory is that repetitive, high dose consumption of similar foods on a

continuous basis--in addition to the preservatives, food coloring agents, flavor

enhancers and antibiotics--all create an environment in which the immune

system begins to react against these conditions. (7) An additional speculation

is that infrequent food rotation (it is often said that most people eat the same

10 foods every week) may predispose a person toward the development of

hypersensitivity. This occurrence in addition to insufficient digestion of food

proteins into their basic structures allows partially degraded proteins that

retain their antigenicity to enter the systemic circulation, provoking the

immune system into responding as if encountering a foreign protein.

Testing of patients with immediate-onset allergy symptoms uncovered a

correlation between both types of allergic reactions, as anti-allergy antibodies

of both immediate (IgE) and delayed (IgG) reactions were detected in their

sera, an indication that allergenic foods are not always limited to immediate

onset immune reactions; a delayed-type immune reaction can occur as well.

(8) The occurrence of allergic reactions in the intestines caused by foods is

documented with altered transport of food proteins across the intestinal wall

(via increased secretion and/or decreased absorption), increased

permeability and motility of the intestine. (9) This occurrence coupled with

intestinal infections and a decrease in secretory IgA may serve to alter

intestinal permeability, resulting in increased antigenic substances interacting

with the immune system. Increased antigenic load coupled with an allergic

predisposition, or sensitivity to certain foods may foster the development of

adverse immunologic reactions to foods.

Food comprises the largest source of antigenic challenges to our immune

system. (10) Technically, food allergy is defined as a grouping of clinical

signs

and symptoms that result from the body's sensitization to one or more foods

wherein symptoms may manifest at any place in the body as a result of

immediate or delayed allergic reactions and their byproducts. As mentioned

previously, a person may not notice the appearance of symptoms until several

hours or days later. And because of the frequency with which similar foods

are consumed, allergic reactions are continuously overlaid. The

acknowledgement of food allergies and the symptoms it causes has received

little attention in mainstream medical practice until relatively recently. Many

patients who are tested and work to purge their diets of offending foods are

finding relief from their previously unexplained symptoms. The following is a

brief listing of the more common food-related symptoms seen in allergic

patients; it is neither inclusive nor exclusive of the symptoms a person may

experience with food allergy.

* Aches and Pains

* ADHD

* Anxiety

* Arthritis

* Asthma

* Bloating

* Celiac Disease

* Chronic Fatigue

* Chronic Infections

* Dizziness

* Eczema

* Enuresis (Bed Wetting)

* Fibromyalgia

* Hyperactivity

* Irritable Bowel Syndrome

* Lethargy

* Migraine

* Nausea

* PMS

* Psoriasis

* Recurrent Ear Infection

* Recurrent Sinus Infections

* Rhinitis Sinusitis

* Urticaria

A common, debilitating health issue, food allergies are costing people with

repeat medical exams and tests with no answers, and lost productivity and

quality of life. Additionally, the identification of food allergies are

important

because of their indirect toll; if one's body is constantly struggling to deal

with

what appears to be a foreign invader, large amounts of energy are spent by

the immune system trying to defend the body. Although speculative in nature,

if the immune system is constantly engaged in fighting food proteins (which

are generally harmless-it is the body's reaction that leads to symptoms),

immune surveillance may be decreased, allowing for other immunologic

problems to creep up, such as cancers or autoimmune conditions. (Will a'

'distracted' immune system be less able to recognize new cancer cells? Will

an over-stimulated immune system lead to autoimmunity, in which the body

begins to attack itself?) Theoretical in nature, these are important questions

to

ask, and science has much to learn in this regard. However, if these scenarios

are even somewhat of a possibility, removal of food allergies becomes a high

priority.

Testing for Food Allergies: Identification

Modern serum testing used in conjunction with a detailed history and

symptom picture can be utilized to gain a rapid and accurate picture of a

patient's food allergies and sensitivities. Prior to the advent of expeditious

and

accurate food allergy tests, it was difficult to definitively establish what

foods

were the cause of allergic symptoms in patients due to the confounding

nature of food elimination and reintroduction; not all food allergies and

sensitivities are immediately manifested, some take several hours to days to

create symptoms. Testing a patient with antigenic foods, either through oral

consumption or in a skin test, are more difficult for the patient, dangerous in

that severe reaction crises may occur, and skin testing does not reveal the

true nature of the allergy; food proteins react differently in the skin than in

the

gastrointestinal tract; these can be two different types of allergy.

Skin Testing

Skin tests for allergies are based on the size of the swelling, or wheal that is

formed in reaction to injection of purified proteins. A positive result will

produce a localized, pruritic (itchy) wheal and redness that becomes most

established 15-20 minutes following introduction. This type of test is used

most commonly in the diagnosis of patients with allergic respiratory diseases

that have symptoms of cough, sneezing, wheezing, and nasal congestion.

Using this type of testing is appropriate for the establishment of IgE-mediated,

or immediate onset allergy that can occur anytime within 2 hours of ingesting

the suspected food. Testing for other food allergies (delayed onset) via skin

introduction will not establish this diagnosis. Delayed onset food allergies

occur after a food protein has been distributed throughout the body;

introduction of a suspected delayed onset allergenic food into the skin will not

recreate previously observed allergic symptoms when this food was

consumed orally. (11) People wanting to know if they have delayed onset

food allergies should not undergo this type of test. However, verification of an

immediate onset food allergy can be made using skin prick testing. This

testing is usually offered by an allergist, and is quite difficult for the

patient to

undergo. That being said however, knowing which foods a patient may

acutely react to could save their life, if it is identified within the

sensitivity and

specificity parameters of this particular testing model.

Elimination-challenge diet

Oral provocation with foods suspected to be allergenic to the patient has been

used in the past to determine food allergy. Although this test has some utility,

it is very difficult to administer and confirm results, as mentioned above. It

is

necessary for patients to remove all suspected food allergens, which is in

itself unreliable, as just as many non-suspect foods as those that are suspect,

can cause allergy. Keeping in mind that this type of food allergy testing is not

recommended for patients to do themselves (due to the danger of

reintroducing a food allergen and the possibility of a dangerous allergic

reaction requiring medical attention), the objective of this testing is to

uncover

delayed onset reactions. This is often difficult to establish due to the nature

of

delayed onset reactions occurring anywhere from hours to days after

ingesting the allergenic food. Differentiating which food caused what

symptom is difficult, and usually highly inaccurate. This type of testing can

provide some positive results in the process of revealing allergenic/irritating

foods, however when patients continue to experience symptoms despite

removing the offending foods, a more precise form of testing is indicated. The

accuracy of removing the most highly mentioned allergenic foods such as

wheat, corn, soy, and dairy requires an immense attention to detail; even

some foods that do not contain such items can have them listed on the

package label in other forms that the consumer may not be aware of, and on

some food labels, the mention that the food is made in a factory that

processes another type of food leads to the awareness that there may be no

entirely sureproof way to remove allergenic processed foods from the diet.

Enzyme linked immunosorbent assay (ELISA)

The previously mentioned food allergy detection techniques are rapidly

becoming outmoded as newer, more precise technology becomes widely

available. ELISA is an easy, and powerful method that can be used to detect

antibodies in serum, urine and other materials. Because it is highly reliable in

detecting antibodies (reflecting immune response to allergies), this method is

often used in diagnostic food allergy testing. ELISA assay is a very sensitive

test, and has the ability to measure IgA, IgE, IgG, and IgG4 antibodies,

revealing the nature of suspected allergens as immediate or delayed onset.

Previously, obtaining food allergy testing utilizing ELISA technology via

allergy testing was only possible through a doctor's visit, meaning the patient

had to visit the physician, and have blood drawn which was sent out to a

laboratory; after the doctor visit and testing, hundreds of dollars could be

spent for the diagnosis of food allergies.

People who suspect they have food allergies can obtain accurate food allergy

testing in their own homes using ELISA technology. Available exclusively

through Health Dynamics, patient-directed food allergy testing kits lets the

patient obtain their own blood sample (only 2 to 3) drops of blood are

required (the kit contains an easy to use auto-lancet) that can be sent directly

to a laboratory that will test the blood twice (to ensure accuracy of results)

for

food allergies. People can order this kit themselves; no doctor's prescription

is

required. The process tests the 96 most commonly consumed foods,

providing information on antibody levels against foods in the following

categories: dairy, seafood, poultry, meats, vegetables, nuts and grains, fruits,

and miscellaneous food items such as coffee, honey, sugar, etc. A detailed

report is sent back to the patient providing information on foods that caused

no reaction, low, moderate, and high reactivity, and which type of reaction

(IgE-immediate or IgG-delayed) the food registered. A user's guide with

explanation of the test results is provided, along with a personalized dietary

guideline protocol designed to assist the patient in techniques for removing

offending foods, and suggestions of foods that can be added to the diet safely.

Depending on the reactivity of the foods, some foods should be avoided for a

period of 3 to 9 months after which these foods may be cautiously

reintroduced and eaten on a strict rotation basis, to avoid recreating the

allergy/sensitivity. Foods that register as highly reactive should be avoided

entirely. Upon removal of the reactive foods, patients may not notice a

complete absolution of symptoms until several weeks later. As most food

allergies are delayed onset, the reactive antigen-antibody complexes must be

cleared from the system, a process that can take some time.

Summary

Diagnosis of food allergies requires some detective work on the part of the

patient. The acknowledgement that foods cause allergy symptoms (as well as

symptoms that are not always ascribed to typically allergic reactions) is

becoming more accepted and greater technology is now available offering

ease of diagnosis. Standard means of unveiling food allergy (skin prick, food

elimination/challenge) do not always provide the sensitivity and specificity

needed to accurately identify allergenic foods and delayed onset allergic

reactions, and both are quite laborious to undertake. Home allergy testing

offers a way for patients to obtain an accurate picture of foods they may be

allergic to, without having to play a game of roulette when avoiding and

challenging foods, or perhaps having a delayed-onset allergy missed in a

skin prick test.