Food allergies

Many people suffer a reaction to a certain food and then label themselves as allergic, to the extent that some alter their diet so drastically that it becomes unbalanced. What is food allergy, what is food intolerance, and what is the difference? Can they be prevented, and is there any treatment other than avoidance?

In technical terms:

An adverse food reaction is an umbrella term meaning any adverse reaction to food.

Food allergy means any adverse reaction due to an allergic mechanism. It may be immediate, and can vary from tingling around the mouth with the development of an itchy rash [urticaria] to rapid swelling of mouth and tongue with a systemic reaction that can be fatal. This is mediated by an IgE reaction [Ig.. means the type of immune globulin produced; different ones have different functions in the body]. Another kind of food allergy, mediated by IgG, has a delayed reaction a day or 2 after eating the food. While some IgE food allergies may be acutely life threatening, those mediated by IgG tend to be less dramatic and may be unrecognised.

This article will concentrate on IgE food allergies.

Food intolerance means any adverse reaction due to physiologic or non-allergic mechanisms, in other words due to toxic, idiosyncratic, pharmaceutical or metabolic factors. Reactions may be in the GIT, respiratory system, skin or nervous system. Diagnosis is by history and food challenge, and skin and blood tests are of no use e.g. lactose intolerance where drinking milk causes diarrhea due to lack of lactase in the gut. We will look at this in the next article, as well as IgG reactions.

Who gets food allergies?

The incidence is 5-8% in children and 1.5% in adults, but is increasing, having risen in children by 18% from 1997-2007! Development of food allergy depends on genes, exposure, gut permeability,[which is greater in infancy], and environmental factors such as exposure to bacteria; a study done in 2001 suggests that increased cleanliness increases the incidence of atopy by affecting the infant’s GI flora [the bugs residing in the gut] and the maturation of the immune system.

Allergies can affect anyone, but both atopy [i.e. asthma, hay fever, and/ or eczema] and obesity are associated with a higher incidence; atopic children have a 35% increased incidence of food allergy. The May 2009 "Journal of Allergy and Clinical Immunology" published a study suggesting that increasing childhood obesity was associated with a greater development of atopic disease such as eczema, and a huge 59 % increase in food sensitization!  Researchers in this study noted, "The analysis of continuous Body Mass Index (BMI) with total IgE levels supports the concept that increased weight is associated with increased allergic predisposition.”

Other studies have also associated food sensitivities to being overweight. In the Journal “Experimental and Clinical Endocrinology and Diabetes,” researchers looked at two groups of children: In normal weight children, inflammatory markers were normal, and there was no increase in IgG antibodies. Overweight children had both raised levels of an inflammatory marker and IgG antibodies.

Exposure to allergy producing substances can be pre- or post natal and may be by inhalation or ingestion,- even through breast milk, e.g. peanut ingestion by a mother in pregnancy or while breast feeding can increase the likelihood of peanut allergy in the infant. Exposure can be additive and is also influenced by other environmental factors such as tobacco exposure, stress etc.

More than  85% of food allergies are due to either milk [cow’s milk allergy has a 2.5% incidence in the 1st 3 years of life], egg, soy,or wheat  in children, and peanut, nuts, wheat, shellfish, and fish in adults.

 How is it diagnosed?

Diagnosis of allergy is primarily by the history, and a food and symptom diary can be helpful. Lab tests may be done to exclude infection and to look for other causes of the symptoms such as diarrhoea. Tests for specific allergies include ‘Pharacia CAP Fluorescein Enzyme immunoassay’ [CAP-FEIA] which is almost 100% accurate for wheat, 86% for soy and 90-100% for milk, egg, fish and peanuts, and is replacing Rast and Elisa.

Skin tests are more economical and give results within 30 minutes, [a positive result being a wheal of greater than 3mm]; a negative accurately suggests the absence of IgE mediated allergy. The test is especially useful for milk, eggs, soy, peanut, cod and catfish, which account for 80% of all of this kind of food allergy. [Increased IgE levels themselves are not necessarily related to atopy, and symptoms are only seen in 30-40% people who test positive.]

The gold standard is the double blind food challenge: This is done once all symptoms are resolved and the patient is on no anti allergy treatment.  1 food is introduced each day, and increasing amounts of the food are given every 30 -60 minutes until symptoms appear. Usually 60-100gm food, or 10gm pure protein isolate is safe and sufficient to cause a reaction. A patient must be observed for 2-3 hours after the challenge, even when the results were negative in case of a later reaction.

A simple test that you can do yourself involves taking your pulse rate after eating a food to which you feel you may react. First take your pulse for 1 minute at rest, then put the suspect food in your mouth. If your pulse rate increases by 10 beats or more despite resting, that food is suspicious.

IgG testing is also now being looked at and research is starting to confirm its usefulness. It is used for uncovering delayed or hidden food allergies, which are the most common type of food sensitivity. Doctors who specialize in alternative medicine tend to use labs where IgG testing is performed. I will discuss this further next time.

There are many other tests on the market whose reliability is unproven, such as Alcat.

What is the usual Treatment?

Prevention is always better than cure, and Probiotics are being shown to be of benefit when given prenatally to mother and for 6 months after birth, especially when associated with breast feeding. Prevention is best achieved by exclusive breast feeding for at least the 1st 6 months of life, then progressing onto a protein hydrolysate or amino acid formula. Allergy causing foods such as milk, egg, nuts and fish should be avoided until 3 years of age. As sensitisation can occur via breast milk due to allergens in mother’s diet, she should try to avoid milk, egg, peanut and soy.

Many children outgrow their allergies after about 2 years, especially wheat, milk, soy and eggs, and so allergic children should be rechallenged every 6-12 months after age 2.

Once the allergy is established, the offending food must be avoided. In the case of severe allergies this can be life saving, and any child with life threatening reactions needs special monitoring at school to ensure there is no food sharing. Staff and any caregivers must be fully informed and know what action to take should a mishap occur. For such sufferers a ready loaded adrenaline pen is available [Epipen], which should be carried everywhere with the sufferer, who should also wear a Medic Alert bracelet.

Desensitisation: When allergy injections have been attempted for food allergy, the rate of severe allergic reactions was too high to continue the studies. More recently, research has focused on giving the same type of treatments by mouth, called oral desensitization. Although this appears safer than injections for food allergy, there continue to be safety concerns due to high rates of anaphylaxis [ severe allergic reaction].There are 2 main methods for oral desensitization: Oral immunotherapy (OIT) involves feeding small amounts of the allergen. This can desensitize individuals with food allergy, but side effects including anaphylaxis, are common and unpredictable.
Sublingual immunotherapy (SLIT) involves placing a small amount of the allergen under the tongue. Experience is limited with this technique; however, early results suggest it may have a better side effect profile. Both these and other methods are still being researched, and require specialist supervision.  In most cases, these treatments do not cure the food allergy but may offer a degree of protection as long as the person is taking the treatment, which may enable some people to eat larger amounts of a problem food before experiencing symptoms and thus provide some protection against hidden exposures.

What Other treatments are available?

A healthy diet, avoiding highly refined carbohydrates and sugars, will help protect the immune system.

Omega-3 fatty acids: a German study published in the journal Allergy found people who have diets rich in omega-3 fatty acids suffer from fewer allergy symptoms. A second study in Sweden found that children who regularly ate fish prior to age one had much lower allergies by age four. The best sources of omega-3 fatty acids are grass fed meat, free range or omega 3 fed eggs, and krill oil, or omega 3 oil supplements can be obtained from a health shop. (Fish has become rather contaminated to rely on as a staple, but sardines and pilchards are a good cheap source.)

Probiotics: In a 2008 study, researchers discovered that people who took probiotics throughout the allergy season had lower levels of an antibody that triggered allergy symptoms. They also had higher levels of a different antibody (IgG), thought to play a protective role against allergic reactions. Healing the gut, getting the healthy bacteria back to normal, eating a healthier diet to decrease inflammation by reducing refined sugar intake may prove very helpful for patients.
Vitamin D: Insufficient vitamin D levels have been linked to more severe asthma and allergies in children. Vitamin D has also been found to reduce allergic responses to mold.

Locally produced honey: Many believe that consuming locally produced honey, which contains pollen spores picked up by the bees from your local plants, can act as a natural “allergy vaccine.” By introducing a small amount of allergen into your system (from eating the honey), your immune system is activated and over time can build up your natural immunity against it. Just be careful to consume honey moderately as it’s high in fructose.

A cause for worry
There is growing concern over a worldwide association between obesity and asthma-related diseases with the other health consequences mentioned above. While no one is clear on the exact mechanics of how they are connected, food allergy may be entwined between them, as well as increased inflammation, hormone changes, poor nutrition and other possible factors. It is uncertain if food allergies are the cause or result of being overweight, but they certainly cause extra stress on an already stressed body. An overweight person with food allergies may struggle to decrease inflammation, eradicate illnesses like asthma and get blood sugar under prompt control. It seems that removing the allergic foods may help reset the body regulation so it can lose weight more easily, and help promote general well being.

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