Food Allergy – When Foods Become a Threat

Typical symptoms of food allergies

The symptoms of a food allergy manifest on the skin and mucous membranes, in the digestive tract, or through breathing problems. A combination of various symptoms is also possible. Initial allergy symptoms may appear within minutes after contact with the triggering food or may take several hours to manifest. The intensity of the reaction can depend on the severity of the food allergy and the amount of allergens consumed. In cases of mild food allergies, consuming small amounts may not trigger any noticeable reactions. For instance, someone who is mildly allergic to legumes might not experience any symptoms from eating a few peas in a stir-fry.

• Mucous membranes: Symptoms of food allergies most commonly affect the mucous membranes, particularly the mouth, which comes into direct contact with the allergen during food consumption. An unpleasant tingling and itching sensation may affect the throat and palate. Swelling of the mucous membranes in the mouth is also possible. These symptoms occur immediately after contact with the allergen, for example, just minutes after eating an apple.
• Digestive tract: The digestive system can react to allergens with symptoms such as nausea, stomach pain, diarrhea, and vomiting. These symptoms subside once the allergens have been completely expelled from the body.
• Respiratory system: The respiratory system can also be affected, often in connection with swelling of the mucous membranes in the mouth. Symptoms may include a dry cough, hoarseness, or a whistling sound when breathing. These symptoms may also indicate other health issues but could be linked to an allergy if they occur within hours of consuming a specific food. In rare cases, food allergies can cause severe swelling of the airways, leading to acute shortness of breath.

Shortness of breath or anaphylactic shock reactions from food allergies are relatively rare. However, when they do occur, they can be life-threatening. It is important to seek medical help immediately in case of any respiratory issues. In the event of shortness of breath or an asthma attack, emergency services should be called, as a severe allergic reaction can be stopped quickly with emergency medications. Once a severe food allergy is diagnosed, patients can carry special allergy emergency kits to administer self-treatment in case of an allergic reaction. For instance, the drug epinephrine can be injected directly into the thigh using an auto-injector, allowing the adrenaline to act immediately to counter an allergic shock.

Why do food allergies occur?

In a food allergy, the immune system attacks certain proteins found in food, mistakenly identifying them as harmful. In most cases, allergic symptoms are triggered by immunoglobulins (IgE), which are antibodies that usually help protect the body from viruses, bacteria, and other harmful substances. These IgE antibodies cause the typical food allergy symptoms described earlier. In rare cases, allergic reactions can occur without IgE antibodies, which often results in gastrointestinal symptoms.

Food allergies are different from food intolerances. Autoimmune diseases or digestive system disorders can also cause symptoms similar to food allergies. For example, lactose intolerance occurs when the body is unable to properly digest lactose (milk sugar). Celiac disease is an autoimmune disorder where the immune system attacks the body's own cells after consuming gluten. However, this is not a food allergy.

In some cases, toxic reactions can cause symptoms that resemble allergies. For example, mold spores in food can lead to vomiting, diarrhea, or poisoning symptoms. Mold cannot be rendered harmless by boiling the food.

Common food allergy triggers

The following foods and food components are known as common triggers for food allergies and food intolerances. They must be listed on product packaging by law. Stores selling these foods unpackaged must also warn customers about potential allergies.

• Eggs
• Peanuts
• Fish
• Shellfish
• Lupins
• Milk
• Tree nuts
• Celery
• Mustard
• Sesame seeds
• Sulfites (preservatives in dried fruit or wine)
• Wheat, rye, oats, and other gluten-containing grains

Among the allergy triggers listed above, peanuts, tree nuts, wheat, eggs, and milk cause the most allergies. Regarding milk, it is important to note that lactose intolerance is sometimes mistaken for a milk allergy. True milk protein allergies are more common in young children but usually subside within a few years. Milk allergies in adults are rare. However, food allergies to tree nuts or peanuts can last a lifetime. Peanuts, in particular, are known to trigger severe allergic reactions from even small amounts.

Generally, food allergies that do not disappear by puberty are likely to persist into adulthood. Additionally, some food allergies only develop in adulthood. Examples include allergies to fish or shellfish, which are extremely rare in children, and wheat allergies, which often manifest after childhood and adolescence.

Cross-allergies between food and other allergens

People with food allergies may develop a cross-allergy to certain pollen. Conversely, people with pollen allergies sometimes react to specific foods. The birch tree is the most well-known example of cross-allergies with food. People allergic to birch pollen often develop food allergies to apples or other fruits. When birch pollen is in the air, it can act as a trigger for these food allergies, intensifying the symptoms experienced when eating fruit. Another example is the combination of house dust allergies and shellfish allergies, although this occurs far less frequently than pollen-food cross-allergies. The latex-fruit syndrome is another cross-reaction that can occur in people allergic to latex after consuming certain fruits, vegetables, or nuts.

Other factors can also exacerbate food allergies. Alcohol consumption or taking certain medications can amplify symptoms. Physical exertion or infections may also cause more severe reactions to food allergies.

Diagnosis and treatment of food allergies

The challenge with food allergies is that their symptoms can resemble many other conditions or allergies. The roughly four percent of the population affected by food allergies often struggle with their symptoms for a long time before receiving an allergy diagnosis. To diagnose food allergies, doctors typically use a combination of different allergy tests, preceded by in-depth patient interviews.

• Prick test: One of the most reliable skin tests, the prick test is commonly used to diagnose various allergies. A drop of liquid containing the allergen is applied to the skin, which is then pricked with a sterile needle. If the person is allergic, the allergen will penetrate the skin, causing a reaction (such as redness, swelling, or hives) within a short time. Several allergens are often tested at once on numbered and prepared skin areas.
• Blood test: If the patient’s history suggests a severe food allergy with potentially dangerous consequences, a blood sample may be tested instead. Blood tests are completely safe for patients at risk of severe reactions from skin tests. IgE antibodies, which indicate an allergic reaction, can be detected in the blood. However, IgE can also be elevated due to other conditions, so blood tests alone do not always provide a definitive food allergy diagnosis.
• Provocation test: A provocation test can confirm a diagnosis when blood or skin tests do not provide conclusive results. However, this test must always be conducted under medical supervision. During a provocation test, the patient consumes a small amount of the suspected allergen, such as eating a tiny portion of a suspected food allergen. Allergic reactions during the provocation test can be severe, but in an allergy clinic, immediate countermeasures can be taken. Understandably, this is not the preferred method for diagnosing food allergies.
• Elimination diet: This special diet typically accompanies diagnosis to confirm the results of blood and skin tests. The suspected food allergens are completely eliminated from the patient’s diet for several weeks. After this period, the allergens are reintroduced in a controlled, medically supervised setting. If the patient exhibits allergic symptoms, the elimination diet can serve as a guide for a long-term dietary adjustment.

Once a food allergy is confirmed, specific steps can be taken to avoid the allergen in the future. Medications can offer short-term relief for severe symptoms, but the long-term solution is to adjust the patient’s diet under medical guidance to avoid the allergen altogether.

For children and adolescents, some food allergies may disappear over time as the immune system learns to tolerate the previously "hostile" proteins. Milk, soy, and wheat allergies are known to often subside or disappear during childhood. Therefore, it is advisable to repeat allergy tests in children and adolescents periodically. However, when adults develop a food allergy, the immune system usually does not learn to tolerate it. Food allergies in adults are rare but typically permanent.

Nutritional supplements as a balance for food allergies

Some foods can easily be avoided—nuts or shellfish, for example, are not necessary for a balanced diet. However, avoiding foods that provide essential vitamins, magnesium, folic acid, and other critical nutrients can lead to deficiencies. For instance, eliminating dairy products entirely can result in a lack of important nutrients, which could be particularly harmful to growing children. People who are ill or elderly may also require increased amounts of certain nutrients.

Nutritional supplements can help maintain the intake of essential vitamins and minerals during a dietary adjustment. Omega-3 fatty acids, found in fish and some seeds and nuts, are an example of supplements available in pill or effervescent tablet form. Discuss the potential use of supplements with your doctor as part of your food allergy treatment plan.

Desensitization for a food allergy?

A desensitization process, similar to treatments for hay fever or pet allergies, is not yet available for food allergies. Some studies on various food allergies have made progress, but it may still take time before these become approved medical procedures. Currently, in mid-2024, a study in the UK is underway in which children are consuming small amounts of foods they are allergic to under medical supervision. According to the BBC, one boy with a peanut allergy has even been able to eat up to six peanuts per day without any symptoms.

This method carries the risk of allergic overreactions, and there is no long-term data yet. Additionally, those who undergo such treatment will likely need to continue consuming small amounts of the allergen for the rest of their lives to maintain their tolerance. The success of these studies will need to be demonstrated over many years. If you notice symptoms of a food allergy, it is always advisable to seek specialist medical advice. Many general practitioners, pediatricians, dermatologists, or ENT doctors are also allergists. Take your symptoms seriously and seek professional help, as it is possible to live well with a diagnosed food allergy.