Topic 2 Most Severe Allergy Symptoms

Eczema is one of the strongest risk factors for food allergy. In a study by Martin et al., one in five young children with eczema has had challenge-confirmed allergy to egg white or sesame by 12 months of age, compared to only one in 25 children without eczema (ibid.). In addition, those with earlier age of onset eczema (first 3 months of life) and increasing severity of eczema (based on treatment required for control) were more likely to develop a food allergy (ibid.).

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In child patients, three different clinical reaction patterns can be differentiated as follows:

  • immediate-type reactions
  • isolated late eczematous reactions
  • combined immediate-type and late eczematous reactions

Therefore, prevention of eczema in early life may prevent the development of future food allergy and other allergic diseases. However, it is yet to be determined whether prevention of eczema in early life will subsequently prevent allergic sensitisation and food allergy.

Another type of delayed food allergy reaction stems from food protein-induced enterocolitis syndrome (FPIES), a severe gastrointestinal reaction that generally occurs two to six hours after consuming milk, soy, certain grains, and some other solid foods. The enterocolitis syndrome mostly occurs in children exposed to these foods for the first time or who are being weaned. FPIES often involves repetitive vomiting and can lead to dehydration. In some cases, babies may develop bloody diarrhoea. Because the symptoms resemble those of a viral illness or bacterial infection, diagnosis of FPIES may be delayed. FPIES is a medical emergency that should be treated with IV rehydration. Unlike other food-allergic reactions that can trigger an allergic response throughout the body, the symptoms of FPIES typically are confined to the gastrointestinal system.

Symptoms may include:

  • Severe vomiting
  • Diarrhoea (sometimes bloody)
  • Weight loss
  • Dehydration
  • Lack of energy
  • Failure to thrive

Vomiting and diarrhoea may not occur until several hours after the offending food is consumed, so a link between the symptom and the food may not be immediately apparent.



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Talking about food allergies and reactions, you should be aware about the phenomenon of cross-reactivity. This event occurs when the body’s immune system identifies the proteins, or components, in different substances as being structurally similar or biologically related, thus triggering a response. When a person comes into contact with either, whether or not it is a protein in something that the person involved is truly allergic to, the immune system can react in the same way, which in some cases can cause allergic symptoms.

Examples of food families with high rates of cross-reactivity are:

  • mammalian milks
  • eggs
  • fish
  • shellfish
  • grains: wheat, barley, rye but in a more restrained quantity

The diagnosis and management of food allergies is complicated by an abundance of homologous, cross-reactive proteins in edible foods and aeroallergens. At the same time, many are sensitized to foods without exhibiting clinical reactivity.

Finally, food handlers should be aware that…

Not everyone who experiences symptoms after eating certain foods has a food allergy or needs to avoid that food entirely; for instance, some people experience an itchy mouth and throat after eating a raw or uncooked fruit or vegetables. This may indicate an oral allergy syndrome – a reaction to pollen, not to the food itself. The immune system recognises the pollen and similar proteins in the food and directs an allergic response to it. The allergen is destroyed by heating the food, which can then be consumed without problems.

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Anaphylaxis, (also known as an anaphylactic reaction) is a severe, potentially life-threatening allergic reaction which may occur due to a variety of causes, with food allergy being its main cause. During an anaphylactic episode, symptoms may affect several areas of the body, including breathing and blood circulation. Usually, the episode begins within minutes after the allergen consumption, and less commonly, hours later. Up to 20% of patients have a second wave of symptoms hours or even days after their initial symptoms have subsided. This is called biphasic anaphylaxis.

Anaphylaxis is highly likely to occur when any one of the following happens within minutes to hours after ingestion of the food allergen: upon exposure, a person may have symptoms that involve the skin, nose, mouth (e.g., skin symptoms or swollen lips), or gastrointestinal tract (e.g., vomiting, diarrhoea, cramping), along with difficulty breathing and/or reduced blood pressure (e.g., pale face, weak pulse, confusion, loss of consciousness).

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