18 January 2005

The lowdown on maize allergies

Most people are aware of common allergies like wheat, peanut and milk allergies, but maize allergy, which is admittedly less common, is also an allergy that should be kept in mind.

Most people are aware of common allergies like wheat, peanut and milk allergies, but maize allergy, which is admittedly less common, is also an allergy that should be kept in mind when adults and children present with allergic symptoms.

Recent research indicates that maize allergy may well be underdiagnosed and responsible for slightly more cases of allergy than was previously believed. Given that maize is one of the most important staple foods in South Africa, and that maize-derived products are widely used in food processing, this is an allergy that South Africans need to be more aware of.

Symptoms of maize allergy
Maize allergy can cause serious reactions, such as anaphylactic shock (swelling of the face, problems with breathing, low blood pressure, irregular heartbeats, hoarse voice, feeling hot and flushing), but these reactions are relatively rare.

More common symptoms include abdominal pain, nausea, vomiting, atopic dermatitis, the so-called "oral allergy syndrome", and recurrent serious otitis media (infection of the inner ear).

It is important to keep in mind that individuals may react to eating maize and maize-derived products, but also to inhaling maize dust, and being exposed to maize powder (e.g. some latex gloves contain maize powder).

If you suspect that you may have a maize allergy because you develop some, or all of the above-mentioned symptoms, and cutting out wheat does not improve the situation, you need to ask your medical doctor to send you for allergy tests (IgE skin and blood tests are generally used).

Foods that contain maize

Maize is problematic because of two reasons:

1) Maize is eaten in a variety of ways:

  • as a vegetable (corn on the cob and sweetcorn)
  • as maize meal
  • as maize derivatives (maize or corn oil, corn syrup, cornstarch, corn flour, cornmeal)

2) Many processed food products contain some form of maize

Maize may be found in all of the following foods:

  • fresh maize or corn (a popular way of eating maize in South Africa)
  • maize meal for making porridge (the most important use in South Africa)
  • dried, crushed maize (samp, of corn grits)
  • canned sweetcorn
  • cornflour or corn starch (Maizena)
  • cornflakes (check other cereals like muesli for maize content)
  • popcorn and caramel corn
  • maize snack foods, including Mexican tortillas, NickNacks and Doritos
  • infant formulas
  • polenta
  • canned fruits (the syrup may be thickened with maizena or the fruit itself may cross-react - see below)
  • cookies, cakes
  • jams, jellies, syrups
  • sweets, especially marshmallows
  • cold meats (maize flour may be used as a binder)
  • whiskey, beer and other alcoholic drinks may contain maize or related cereals

Plus commercial uses such as:

  • corn sweetener
  • corn syrup
  • corn alcohol
  • baking powder
  • dextrates, dextrins, maltodextrin
  • flavouring (especially caramel)
  • vegetable gum and paste
  • food starch or modified starch
  • vegetable protein or hydrolysed vegetable protein (HVP), hydrolysed plant protein (HPP) and textured vegetable protein (TVP), though usually made from soya, can also be produced from maize

If you have been diagnosed with maize allergy you need to check every single food label to make sure that the processed foods you purchase do not contain any of the above-mentioned products.

Maize-free diets
Maize-free diets are particularly difficult to handle because so many foods contain some form of maize.

It is always advisable to consult a clinical dietician to help you work out a diet that is free of maize, but still provides you with sufficient nutrients to prevent deficiencies and maintain good health. This is particularly important in infants and children who have increased nutrient needs for growth and development.

The problem becomes even more complex if you are using maize as your staple food, so consult a dietician to steer you through the problems of eliminating maize from your diet in case of a maize allergy.

Cross-reactivity is a situation where an individual who is allergic to a specific food, such as maize, also reacts to other foods and/or plants. You may not fall into this category and be exclusively allergic to maize, but it is something to keep in mind if you have tested positive for maize allergy.

The following foods may cross-react and cause symptoms in people with maize allergy:

  • wheat, rye, barley, oats, rice, millet
  • peach, apple, apricot, banana and carrot
  • walnuts, hazelnuts, peanuts

A clinical dietician will help you to find foods that you can eat, so make use of their services. For further information, visit - (Dr Ingrid van Heerden, DietDoc)

Any questions? Ask DietDoc


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Allergy expert

Dr Morris is the Principal Allergist at the Cape Town and Johannesburg Allergy Clinics with postgraduate diplomas in Allergology, Dermatology, Paediatrics and Family Medicine dealing with both adult and childhood allergies. obesity and diabetes societies and runs a trial centre for new drugs.

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