Celiac.com 06/29/2009 - Hypersensitive reactions to food are becoming increasingly problematic in society. Allergy experts report that the prevalence of food allergies appears to be rising and while there are no exact figures for this in Australia, some studies have shown marked increases overseas.

For example, a study from the Isle of Wight in the U.K. has shown a tripling in the rate of peanut allergies over the past 10 years. However, the reason for this is not yet clear.  Auckland allergy expert Dr. Vincent Crump has three theories regarding the increase in peanut allergies.

More people are eating peanuts and, up until recently, many eczema creams contained peanut oil, possibly exposing an allergy prone person to the food.

There’s also the 'hygiene theory' of disease, which suggests that children are not exposed to enough dirt and bacteria these days, and therefore do not build up a normal immunity to harmless substances. So when they are exposed, their immune system overreacts and they develop an allergy.

Despite the overall increase in food allergies, the rate in adults is still pretty low – around one per cent. However, the rate is higher in children, where up to five per cent are believed to have a food allergy.

Allergy vs. intolerance

The most common and best understood type of allergy is a reaction in which the body's immune system overreacts to a food and mistakenly produces antibodies (called IgE) to the food.

This can cause reactions, sometimes severe, that affect the skin, breathing, gut and heart.

An intolerance is an adverse reaction to a food that does not involve the immune system. Symptoms are generally less severe, and can include headaches, gut problems and worsening of skin conditions such as eczema. Intolerance is much less likely to be life-threatening than a true allergy.

What is an allergy?

According to the Australian Society of Clinical Immunology and allergy (ASCIA) education resources website, the word “allergy” is frequently overused and misused to include any irritating or uncomfortable symptoms after eating.

Strictly speaking the term should only be used for the symptoms which develop after eating certain foods as part of the immune response.

In an allergic reaction, the body’s immune system mistakenly believes the food is harmful and tries to protect itself. In doing so it overreacts and produces, for example, harmful antibodies to fight the food “allergens”.

In turn, these special antibodies (called IgE) make the body produce histamines and other chemicals, causing reactions that affect the skin, breathing, gut and heart.

IgE antibodies can also “cross react “with other allergens. For example, someone with a latex allergy may also react after eating a banana, kiwi fruit or avocado. According to allergy specialist Professor Rohan Ameratunga, up to 50 per cent of people who react to one tree nut (including almonds, brazil nuts, Cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts) will react to other tree nuts.

A recently recognized form of food allergy is the “oral allergy syndrome”, where a person experiences a cross reaction between pollens and fresh fruit and vegetables.

This “cross-reactivity” is also the reason why some adults with a predisposition to other allergies suddenly develop a food allergy.

For example, a person with a birch pollen allergy can suddenly became allergic to apple or kiwi fruit allergens.

Dr Crump says more and more adults prone to allergies are developing cross reactions after they are overexposed to certain foods (such as acquiring wheat allergies after working in a bakery).

What are the most common food allergies?

Allergies are mostly triggered by nuts, shellfish, fish, milk, eggs, wheat and soybeans.

Adults are more likely to be allergic to fish, shellfish and nuts, with children suffering more from allergies to milk, eggs and peanuts.  Reactions to seeds and fruits are also becoming more common.

There are cultural differences in allergy patterns, according to professor Ameratunga.

In Japan, rice allergy is common. In the Middle East and Australia, sesame allergy is on the rise.

We know the treatment for coeliac disease is a gluten-free diet for life. Although people with coeliac disease produce antibodies the allergic process is different from that seen in most other allergic reactions.

In coeliac disease, gluten reacts with the small intestine, and activates the immune system to attack the delicate lining of the bowel.

The normally rippled lining of the intestine becomes damaged and inflamed, and forms the characteristic flat appearance of celiac disease.

The surface area, which enables the absorption of nutrients and minerals from food, is seriously depleted, leading to gastrointestinal and malabsorptive symptoms.

Common Intolerances

Almost any food can cause an intolerance, but the repeat offenders are;

OFFENDER:
Lactose
FOUND IN:
Milk and milk products. Yoghurts have little lactose and hard cheeses have none.

OFFENDER:
Salicylates
FOUND IN:
Natural food chemicals found in a wide variety of fruits and vegetables such as cauliflower, eggplant, broccoli, tomato, apple, orange, and pineapple. Also found in nuts, spices and aspirin.


OFFENDER:
Amines
FOUND IN:
Histamines and histamine-like chemicals produced during fermentation, and the ageing and ripening of foods. Found in wine, processed meats, hard cheese, tomato paste, chocolate, and many fruits and vegetables.


OFFENDER:
Glutamate
FOUND IN:
An amino acid found naturally in all protein foods such as cheese, processed meats and milk. MSG (additive621) is a type of glutamate, and natural glutamates are also found in soy sauce, broccoli, mushrooms, spinach, tomatoes, grapes, plums and many others foods.

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