Adverse reactions caused by the food we eat can be divided into two groups – allergic (food allergies) and non-allergic (usually also called food intolerances).
Allergies are an exaggerated and inadequate response of the immune system against harmless substances in the environment, which can cause different symptoms.
However, these symptoms are reproducible; that is, they appear whenever the same food (or at least food from the same family) is ingested. In addition, the symptoms are often immediate, occurring minutes to a maximum of two hours after ingestion. In some cases, contact or even inhalation of cooking vapors of the particular food can also cause symptoms.
These symptoms often affect the skin and may appear as red blotches or boils, may cause itching (hives) or swelling, usually on the lips or eyes. They can also cause severe mouth itching, vomiting or abdominal cramps, sneezing, itchy or watery eyes, cough, wheezing, or difficulty breathing.
In some situations, a severe allergic reaction (anaphylaxis) may occur involving several organs simultaneously, such as the skin, the respiratory, digestive and/or cardiovascular systems. In such cases, a sudden drop in blood pressure, sweating, pallor or loss of consciousness may occur. These reactions are life-threatening.
The most common cause of food intolerance is the absence of an enzyme necessary for the digestion of an ingredient in the food or part thereof. A typical example is lactose intolerance, which is due to the lack of the lactase enzyme, a molecule responsible for the digestion of a sugar substance present in milk, known as lactose.
Food intolerance can cause many different symptoms, as it is not one single disease. Symptoms are usually not reproducible or immediate, the most frequent being poor digestion, overeating, bloated stomach, flatulence, heartburn, poor appetite, hair loss, dark circles under the eyes, headaches, among others.
Although an allergic reaction can occur with any food, the food that causes the most allergic reactions is:
• In children – milk protein, eggs, fish, nuts, peanuts, soybean and wheat flour.
• In adults – seafood, fish, nuts/seeds, peanuts and fresh fruits.
A food allergy can occur for the first time at any age, although it is more common in infants and children. In general, when food allergies occur during childhood, they tend to disappear, especially milk and egg allergies. On the other hand, a food allergy in adults tends to persist throughout life.
Food allergies are diagnosed by an immunoallergologist, based on a combination of medical history, skin tests, blood tests and oral tolerance tests.
The only way to prevent allergic reactions is to avoid food containing the specific substance. This means reading labels carefully, being aware of meals in restaurants or food prepared by others. However, it is sometimes complicated to exclude certain substances when their presence is not always visible or correctly marked on packages. This creates anxiety in both patients and their families, due to the fear of accidental exposure.
Together with two medical students from the University of the Algarve, we developed a simple micro-site that quickly identifies the presence of food allergens in packed or frozen food sold in the main supermarkets.
The soualergico.com micro-site is available online and is totally free. It allows the patient to create a shopping list with allergen-free products in different food categories, and also provides additional information on food allergies and intolerance.
By Dr Pedro Morais Silva
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Dr Pedro Morais Silva is an Immunoallergologist at the HPA Health Group: Hospital Particular do Algarve in Alvor, Clínica Particular in AlgarveShopping (Guia) and Clínica Particular SIIPEMOR (São Brás de Alportel).
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