Pathophysiology

Food allergy 

Food allergy is an abnormal immune system reaction to certain foods or ingredients, where the body mistakenly identifies a substance as harmful and triggers an allergic response. Common allergenic foods include peanuts, tree nuts, milk, eggs, wheat, soy, fish, and shellfish. Approximately 1 in 20 children under the age of 5 have food allergies, and they are becoming increasingly more prevalent.

Wheat allergy 

Wheat-Dependent Exercise-Induced Anaphylaxis (WDEIA) is a common cause of adult food-related anaphylaxis in Hong Kong. In this condition, serious and potentially life-threatening allergic reactions occur within 6 hours of wheat ingestion, in combination with cofactors like alcohol, exercise, and non-steroidal anti-inflammatory drugs (NSAIDs).

Celiac disease (gluten intolerance) is an autoimmune disorder triggered by gluten, a protein found in grains, like wheat, rye and barley. Patients may develop symptoms such as abdominal distention, diarrhea or constipation after consuming gluten food products.

Anaphylaxis

Anaphylaxis is a severe, life-threatening allergic reaction that can occur within minutes of exposure to an allergen. Symptoms include difficulty breathing, a drop in blood pressure, a fast pulse, and loss of consciousness.

Symptoms

Mild to moderate symptoms of food allergy:

	Itching or swelling of the mouth, and tightness in the throat or hoarse voice
	Runny nose and watery eyes
	Swelling of the skin, itching, and hives
	Gastrointestinal issues (e.g. nausea, vomiting, and diarrhea)

Severe cases of food allergies may lead to anaphylaxis, which can be life-threatening. Symptoms can progress through several stages:

Stages of anaphylaxis

	Stage 1: Mild symptoms Symptoms are mild and may resemble a common allergic reaction. They can include itching, skin redness, hives, and a runny nose. It's crucial to monitor these signs, especially if you're at risk for anaphylaxis
	Stage 2: Worsening symptoms Symptoms become more severe and widespread. You may experience a rash or hives over a larger area, facial swelling, difficulty swallowing, abdominal pain, vomiting, or diarrhea. Immediate medical attention is necessary at this stage
	Stage 3: Anaphylaxis Symptoms worsen further, leading to breathing difficulties, a weak pulse, chest pain, dizziness, or lightheadedness. Immediate medical attention is required
	Stage 4: Life-threatening symptoms This is the most severe stage, characterized by a significant drop in blood pressure, weak or absent pulse, and inadequate blood flow to vital organs. Without immediate treatment, it can lead to heart attack or death

Test and diagnosis for food allergy

After obtaining comprehensive medical history from patients, the following diagnostic tests may be conducted by the physician if applicable:

	Skin prick test: A common method where a small amount of the suspected allergen is placed on the skin to observe any possible allergic reactions
	Blood test: Blood is first drawn from the patient and afterwards the sample will be exposed to different allergens. The test checks for an increase in IgE antibodies in the blood sample
	Oral food challenge: The suspected food product is directly administered to a patient orally to see if they will develop an allergic reaction or not. This test should only be conducted under the guidance and monitoring of an allergist to ensure safety

Treatment

Antihistamines:

• Mild allergic reactions and symptoms can be relieved using antihistamines (e.g. Diphenhydramine)

Adrenaline：

• Such as EpiPen, it is a lifesaving emergency medication that immediately begins reversing symptoms of anaphylaxis

Avoidance:

• The most effective way to manage allergies is to avoid the known allergenic food entirely

Oral Immunotherapy (OIT):

• A treatment option that helps build tolerance to specific allergens, though it should only be done under medical supervision

Emergency response to allergy reactions

If an allergic reaction occurs, appropriate measures should be taken depending on the severity of the symptoms:

Recovery

If you have food allergy, you can pay attention to the following daily management strategies:

	Keep track of your symptoms: Understand and remember which foods have caused allergic reactions. If you suspect a food allergy, please consult a Specialist in Immunology and Allergy for appropriate testing
	Dietary avoidance: Strictly avoid foods that are known to trigger allergic reactions
	Carry emergency medication: Always carry an adrenaline injection pen
	Inform others: Inform family, friends, and caregivers about your allergies and how to respond in case of emergencies