Are You Dealing With a Corn Allergy or Intolerance?

Negative reactions to corn often go unidentified as people explore more common food culprits. In this article, the author, Dr. Michael Radcliffe, responded to a reader’s post about the difficulty of living with a corn allergy. Dr. Radcliffe was a consultant in Allergy Medicine and Clinical Research Fellow in Allergy Royal Free NHS Trust and the University of Southampton and is in private practice.  He encouraged the writer to be properly assessed and suggested that provocative challenge testing would be advisable to determine if purified corn derivates, such as glucose syrup and maltodextrin, are well tolerated. If this can be shown, he suggested her life would be much easier. This article is adapted with permission from FoodsMatter.com

ROSIE’S POST:

I am sure that I can’t be the only person who is allergic to corn, and it is extremely difficult to ascertain which foods and products are safe for me, as corn is used in many different ways and has many derivatives. Glucose syrup, invert sugar syrup, glucose-fructose syrup, dextrose, dextrin, maltodextrin, xanthum gum are just a few ingredients from corn, and others are even more ambiguously listed: starch, thickener, acid, vegetable oil and natural flavouring could be – and very often are – corn ingredients too. With no clear listing, it makes it almost impossible for someone with corn allergy to eat anything that they have not prepared themselves from scratch using virgin ingredients. (Excerpted)

DR RADCLIFFE:

Corn Allergy

You are right that true (IgE-mediated) corn (maize) allergy is very rare. Symptoms are immediate and conventional (skin prick or specific IgE blood tests) are almost always positive. The internet may give the false impression that corn allergy is common in the US, but almost certainly it is corn intolerance that is mostly being described. A consortium of allergy physicians across Italy, Germany and Switzerland studied true allergy to corn, but managed to find only 23 cases between them. When challenged blind half reacted to 2.5 grams or less of green (unrefined) corn, whilst just two patients reacted to 100 micrograms or less.

Reactions were mild in all but five cases; like Rosie these five appeared to be at risk of corn anaphylaxis. The main corn allergen was found to be a protein, one of a class known as Lipid Transfer Proteins (LTPs). LTPs are vital to plant metabolism being responsible for conveying phospholipids from their site of biosynthesis to cell and mitochondrial membranes that are unable to form them. LTPs are also important to allergy physicians being responsible for cases of allergy and even anaphylaxis due to Rosacea fruits (typically peach) and tree nuts (typically hazelnut).

Corn Intolerance

By contrast I believe corn intolerance to be quite common. Symptoms are never immediate and obvious, and this is why sufferers have never considered corn intolerance to be their problem. Diagnosis is not straightforward, I have never found conventional allergy tests nor any other objective test to be helpful. Sufferers normally present with medically unexplained symptoms and significant quality of life impairment. Diagnosis can be quite challenging; supervised exclusion and challenge starting with a few foods type of exclusion diet is the only validated method. To diagnose corn intolerance, the exclusion diet needs to be followed exactly (e.g. toothpastes contain corn derivatives) and the most severely afflicted sufferers are obviously the better motivated to comply precisely and this limits the application.

If a major reduction of symptoms does not occur after 2-3 weeks on the exclusion diet, it is abandoned. If major improvement does occur, each food is then reintroduced in turn at one or two-day intervals; typical symptoms recurring within a few hours indicating a positive test. Those with corn intolerance are amongst those with the most troublesome and diverse symptoms. Unrelenting headaches and migraine, fatigue and mood disturbances, joint and muscle pains, and upper respiratory symptoms are common. Quite a few will react also to other foods, often milk, often wheat, and the other gluten-containing grains, and in a few cases all the grains need to be excluded to establish full remission of symptoms. I have found corn intolerance to be rather common amongst the hundreds of patients I have placed on exclusion diets during the last thirty years. All are usually delighted to find the explanation for their symptoms and a way, even if tedious, of gaining relief.

Reactions to Corn Derivatives

On a more encouraging note, it is possible that Rosie might find that she does not react to highly purified derivatives of corn. While unrefined forms of corn such as corn-on-the-cob, popcorn, and cornflour will contain sufficient protein to cause allergy, corn oil is unlikely to contain the allergenic protein in sufficient quantity. While glucose syrup, invert sugar syrup, fructose syrup, dextrose, dextrin, maltodextrin and xantham gum may be troublesome to those with corn intolerance (for which we do not understand the mechanism), there is a chance that these would not cause symptoms for those with true corn allergy depending on that individual’s corn allergy threshold and the degree of purification. Hydrolyzed plant or vegetable protein and textured vegetable protein products may cause problems for those with corn intolerance, but whilst they normally contain corn protein, the hydrolysis process denatures this protein making it much less likely to cause allergy.