Getting to know

Food allergy can manifest itself through a variety of symptoms and in different organs of our body. As you would expect, the digestive organs (the mouth, throat, stomach and intestine) are commonly involved in food allergy because they come into direct contact with the food when it’s ingested. However symptoms of food allergy are not limited to the organs involved in digestion. Food allergens absorbed from the intestine, disperse throughout the body via the blood stream and therefore they can trigger an allergic attack in other tissues such as the skin, bronchi, nose, eyes, heart and blood vessels.

Symptoms involving the digestive organs 
Skin symptoms in food allergy 
Organs involved in breathing 
Anaphylactic reactions caused by food allergy

Mouth and throat are frequently affected in food allergy. The most common manifestations are:

• Redness of the lips and the skin around the mouth
• Itching and/or tingling of the mouth, lips and throat
• Swelling of the lips, mouth and throat. You should pay particular attention to these kinds of symptoms because a massive swelling (particularly of the throat) may result in severe breathing difficulties and even an inability to breathe (asphyxia). Such a situation is regarded as an anaphylactic response to food allergens and treated as a major anaphylactic emergency (for more details about the anaphylactic symptoms and emergency treatment please read the section Anaphylaxis).  

A particular form of food allergy in which the symptoms are confined to the mouth and/or throat is called Oral Allergy Syndrome or Pollen-Food Syndrome. This syndrome occurs in up to 70% of people who are allergic to pollens and these people develop mouth and throat symptoms (similar to those listed above) when eating certain raw fruits and vegetables. 

Why should people with pollen allergy develop allergy when eating plant derived foods? 

Scientists have found that some allergens present in pollen grains are common to many plant families. These allergens can also be found in other parts of the plants (such as the stem, leaves, fruits etc). If you remember that every plant develops from a seed which grows inside a fruit, the product of fecundation of a female sexual cell by a male sexual cell (the latter being the pollen) it is not surprising that substances present in pollen grains can be found in other parts of the plant. Different types of plant share common structural components with each other in much the same way that several members of the same family have blue eyes or curly hair etc. Consequently, when a person becomes allergic to a particular pollen allergen, they have a higher chance of developing allergic symptoms when eating a plant derived food containing the same substance. This is called allergic cross-reactivity. To learn more about possible the cross-reactivity between different types of inhaled allergens (pollens or house dust mites) and foods please visit the Allergens section.

Mouth and throat involvement can be the sole manifestations of allergy (as is the case in Oral Allergy Syndrome) or they can precede or accompany symptoms in other organs.

Stomach and intestines

People suffering from food allergy can manifest symptoms of nausea, vomiting, abdominal cramps, and/or diarrhoea when eating food they are allergic to. 

As mentioned above, a particular characteristic of food allergy is that food allergens can be absorbed from the intestine and carried by the blood to other organs where they can trigger an allergic response. 

Very often foods allergens transported by the blood can cause allergic reactions in the skin.

Hives (urticaria or nettle rush) are the most common dermal manifestation of food allergy. These skin symptoms appear at variable time intervals after the culprit food is consumed, usually less than 24 hours. Hives are red, itchy swellings which usually appear without warning and may change location quickly.

Contact urticaria is a particular type of reaction to foods which appears in some people who handle (but do not consume) food which they are allergic to. These people may notice redness, itching, hives or swellings. The symptoms are usually confined to the skin areas that have been in contact with the food. 

Allergic eczema can also be an expression of food allergy, particularly in small children. Allergic eczema manifests itself as red, very itchy inflammation that can develop into blisters (usually small). When the blisters burst, crusts will form.. In small children, these flare-ups can involve the whole body (but usually sparing the diaper/nappy area). In older children and adults, allergic eczema tends to affect limited areas of the skin, typically involving the skin folds (like the elbow joint, around the wrists, behind the knees etc.) 

The symptoms of food allergy can also involve the respiratory organs: the bronchi and the nose. 

Bronchi 
Food allergens reaching the bronchi can trigger an allergic reaction, causing an immediate narrowing of the airways that can vary from mild to very severe. The symptoms experienced in this situation are similar to an asthma attack: dyspnoea (breathing difficulty accompanied by a sensation of lack of air), wheezing sounds which can be heard when you breathe in and out, cough, sensation of chest tightness. The severity of symptoms depends on the severity of bronchial narrowing. In the case of a very pronounced narrowing of the bronchi, passage of the air can be extremely difficult (in some extreme situations the bronchi are so narrowed that the breathing becomes impossible). In this situation immediate administration of drugs which dilate (enlarge) the bronchi is essential. If you experienced this kind of symptoms as a consequence of your food allergy you should consult an allergy specialist without delay. He can recommend the appropriate medication for you and teach you how and when to use it. 

Food induced anaphylactic reactions are the most severe, sometimes life-threatening, manifestations of food allergy. In anaphylaxis, the allergic symptoms are triggered in several organs concomitantly or in a very rapid succession. Urticaria/urticaria-like symptoms are very common manifestations. One or more of the organs mentioned above (mouth and throat, digestive organs, respiratory organs) can also be affected. 

Heart and blood vessels can also be involved in many sufferers, causing palpitations, heart racing and a decrease in blood pressure which manifests as dizziness, sensation of light headedness and, when very severe, even loss of consciousness. 
Catastrophic fall in blood pressure and cardiac arrest, together with severe asthma attacks and asphyxia due to swelling of the throat, are the most important causes of fatal anaphylactic episodes.

Because vital organs may be implicated, anaphylaxis should always be regarded as a potential life-threatening reaction. Anybody who has experienced a food induced anaphylactic reaction should consult an allergy specialist. The specialist will make an accurate diagnosis of the disease; help to identify the culprit food and identify the foods, situations and activities that must be avoided in order to reduce the risk of future attacks. Critically, the doctor will prescribe a treatment and provide you with an emergency management plan (including an emergency treatment), and explain to you the steps you have to take if another anaphylactic attack occurs. To learn more about anaphylactic attacks, their treatment and prevention please visit the  Anaphylaxis section.