Best Way to Understand Ingested (Food) Allergies

An adverse reaction to certain types of food can be either an abnormal response of the immune system to a food protein (a true food allergy), or it can be a chemical reaction to the food that does not involve the immune system (a food intolerance). Food intolerance is a more common condition than food allergy, although some instances of food allergy have been reported in approximately 1-2 percent of adults and in 5-7 percent of children.

Food allergy

True food allergy can give rise either to local symptoms in the stomach and gut, or to more generalized reactions. Contact with food to which you are allergic commonly causes a tingling of the lips and tongue followed by lip swelling (oral allergy syndrome).There may also be stomach cramping, bloating, and diarrhoea. In more severe examples, however, the following symptoms may occur:

• Tongue and throat swelling
• Facial flushing and swelling (angioedema)
• Difficulty in talking and breathing
• Fall in blood pressure causing dizziness and unsteadiness (anaphylaxis)

Food intolerance

Non-allergic food intolerance may be due to the chemical properties of the food or to toxic reactions. Fish, such as mackerel and tuna, have high histamine levels when they start to spoil and these can cause flushing, low blood pressure, and hives a reaction known as scombroid poisoning. And tyramine in red wine and cheese may cause a headache. Headache, along with flushing and gastrointestinal symptoms, can also be related to eating monosodium glutamate (MSG). Milk can cause abdominal pain and diarrhoea in infants. This is brought about by a deficiency in the baby’s bowel of the enzyme lactase, which is necessary for the digestion of lactose, a sugar in milk. This deficiency can occur after a bout of infectious gastroenteritis.

Food additives and colourings may cause hives and make the symptoms of asthma and rhinitis far worse. Such reactions can occur to benzoates, salicylates, sulphites, and tartrazine. If your symptoms begin after eating foods containing preservatives or dyes, such as some cheeses, meat pies, sausages, preserved meat, dried fruit, and canned and bottled food, you should suspect the presence of these substances. Some preservatives are also sprayed on to salads to maintain freshness and can be present in alcoholic drinks and coloured fruit drinks (pop).

Oral allergy syndrome

This occurs in pollen-sensitive people when they eat foods containing a part of a protein structure that is the same as in pollen. The body mistakes the food for a pollen and initiates an allergic reaction. Reactions tend to be mild, confined to the lips and front of the throat, and disappear relatively rapidly. Ragweed- (Ambrosia) sensitive people may have oral symptoms after eating melons and bananas, while those sensitive to birch pollen tend to react to raw potatoes, carrots, celery, apples, hazelnuts, and kiwi fruit.

Atopic eczema

Otherwise known as atopic dermatitis, atopic eczema is the commonest form of allergy suffered by small infants. This disease is generally brought about due to a food allergy to dairy (milk) products or to eggs (generally egg white). Symptoms commonly include:

• Red areas with tiny bumps (papules)
• Blisters that weep
• Scaly skin

In infants, eczema often affects all of the body. As the baby grows and starts to toddle, the pattern of distribution changes, and becomes commonest in the bend of the elbows, at the back of the knees, and over the inside of the wrists. In the most severe cases, atopic eczema can affect any part of the body and cause a distressing, angry inflammation of the skin. The damage to the skin caused by this disease makes the child more susceptible to other environmental allergens, such as those associated with house-dust mites. Two-thirds of children “outgrow” their food allergy by their fourth or fifth year. A child with a food-related allergy does, however, have an increased likelihood of developing asthma and rhinitis.

Coeliac disease

This condition results from a sensitivity to gluten, rather than being an allergy. Gluten is a protein found in cereals such as wheat, barley, oats, and rye. In susceptible individuals, eating gluten produces such symptoms as:

• An uncomfortable bloated feeling
• Wind and diarrhoea
• Malabsorption of food

Children with this disease do not grow as well as their peers, while in adults the malabsorption of food leads to weight loss. Since gluten-containing foods are so much a part of our everyday diet, a stringent programme of avoidance is necessary to avoid chronic ill-health. Gluten-avoidance does, however, result in the complete resolution of all symptoms.