11 May 2023

Food Allergy Testing: Symptoms, Treatments, and When to Consult a Doctor

Food allergy is an immune system reaction occurring from eating some foods. Most times, small amounts of the allergy-causing food can result in an allergic reaction with symptoms such as swollen airways, hives or digestive problems. In certain cases, a food allergy may lead to severe symptoms or a life-threatening reaction called anaphylaxis.

Research shows that food allergy affects about 8% of children below five years and 4% of adults. Although food allergy has no cure, some children outgrow it. Many people mistake a food allergy with a more common reaction called food intolerance. Food intolerance is discomforting but less serious than a food allergy and doesn't involve the immune system.

Symptoms of food allergy

Some people experience an allergic reaction to a particular food. This may be uncomfortable but not severe. In other people, the allergic reaction can be severe and life-threatening. Symptoms of a food allergy often occur within a few minutes to two hours after eating the allergy-causing food. In a few cases, the symptoms are delayed for a few hours.

Common signs and symptoms of food allergy include:

• Abdominal pain, vomiting, nausea or diarrhoea
• Eczema, hives or itching
• Itching or tingling in the mouth
• Trouble breathing, nasal congestion, or wheezing
• Swelling of the tongue, face, lips, throat or other body parts
• Fainting, lightheadedness, or dizziness

Anaphylaxis

Sometimes, food allergy can trigger a more severe, life-threatening reaction called anaphylaxis. The signs and symptoms may include:

• Rapid pulse
• Tightening and constriction of the airways
• Lightheadedness, dizziness or loss of consciousness
• Shock with a severe drop in blood pressure
• A sensation of a lump or swelling in the throat that makes breathing difficult

Food allergy tests

The following tests can help diagnose food allergies.

• Skin prick testing

The skin prick test is a sensitive food allergy testing method that gives a fast result, usually within 30 minutes of testing. In this test, the healthcare professional will prick the front or back of the arm's skin using a sterile probe, then induce a small amount of the suspected allergy-causing food. While this test doesn't cause pain, it is usually uncomfortable.

The test result is positive if an allergic patch develops on the skin. If an allergic patch isn't present, the test is negative. However, the test doesn't determine the level of allergy.

• Blood testing

This blood test is another effective option to diagnose a food allergy. The diagnosis depends on the total number of allergic antibodies present in the blood.

• Oral food challenge

Although the oral food challenge is an effective test, it is expensive. It aids diagnosis of any allergy. The oral food challenge involves eating increasing amounts of the allergic food but under clinical supervision to determine the presence of an allergy and its effect.

Other food allergy testing options are:

• Vega testing
• Kinesiology testing
• Analysis of the hair follicle and scalp
• Alternative blood test

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Treatment

You can prevent food allergy by avoiding the foods that cause your signs and symptoms. Regardless of how hard you try to avoid food allergens,you may still take foods that cause a reaction.

• Minor allergic reactions

You may take prescribed or over-the-counter antihistamines for minor food allergic reactions to alleviate the symptoms. You can take these drugs following exposure to an allergy-causing food to relieve hives or itching, but antihistamines cannot treat a severe allergic reaction.

• Severe allergic reactions

An emergency epinephrine injection or a visit to the emergency room may be necessary when you have a severe allergic reaction. Many people experiencing severe food allergies carry an epinephrine autoinjector (EpiPen, Adrenaclick). This device has a syringe and concealed needle that injects a dose of the medication when pressed against the thigh.

If your doctor prescribes an epinephrine autoinjector

• Ensure you know how to use the autoinjector, including the people closest to you – This could be life-saving if you have an anaphylactic emergency.
• Carry the autoinjector with you always – an extra autoinjector should be at your work desk or car.
• Ensure you replace the epinephrine injector before its expiry date

Experimental Treatment

Research is ongoing to find better treatments that reduce food allergy symptoms and prevent allergies, but there is no proven treatment to relieve or prevent symptoms completely.

A treatment currently studied for food allergy is oral immunotherapy. This treatment involves swallowing or placing small doses of the allergy-causing food under the tongue, then gradually increasing the doses.

One oral immunotherapy drug has been approved to treat children between 4 – 17 years with confirmed peanut allergy, but this medication is unsuitable for those with uncontrolled asthma or other conditions, including eosinophilic oesophagitis.

Lifestyle and home remedies

One way to avoid an allergic reaction is to avoid the food that triggers your symptoms.

• Do not assume

Ensure you read all food labels to ensure they contain no allergy-causing ingredients. Even when you know what the food contains, check the label, as the ingredients may change. Food labels must clearly list if the food product has common food allergens.

Read the food labels carefully to avoid the most common sources of food allergens such as peanuts, fish, soy, wheat, eggs, milk and shellfish,

• When in doubt, do not accept

You are always at risk of eating food you are allergic to at social gatherings and restaurants. Many people do not realise the severity of food reactions and how only a small amount of food can cause severe allergies in some people. If you think a food may contain something that may trigger your allergy, do not eat it.

• Involve caregivers

If your child has a food allergy, inform your relatives, teachers, babysitters and other caregivers. Ensure they understand the importance of your child avoiding foods that cause allergies and what they should do if an emergency occurs.

Informing the caregivers of the steps to take to prevent a reaction is also important such as carefully washing hands and cleaning surfaces that come in contact with any allergy-causing food,

Coping and support

A food allergy may cause concern, affecting work, home and school life. It may also make daily activities that are easy for most families, such as meal preparation and grocery shopping, stressful for peoplewith food allergies.

The following strategies can help manage stress resulting from food allergies.

• Connect with others

Discussing your food allergies and exchanging information with people that have the same concerns may be helpful. Many non-profit organisations and internet sites provide information and platforms for discussing food allergies and issues resulting from it. Some are mainly for the parents of children who have food allergies.

• Educate people around you

Ensure family members and caregivers understand your child's food allergy, including school staff and babysitters.

• Address bullying

Some children get bullied at school because of their food allergies. You should discuss your child's allergy with school personnel to reduce your child's risk of being a target of bullying.

Preparing for your appointment

Doctor's appointments are usually short, and there are usually many things to discuss, so it's important to prepare for your appointment. The information below can help you prepare for the appointment and know what to expect.

• Write down your symptoms, including those that seem unrelated to why you scheduled the appointment
• Write down your details, including recent life changes and major stresses
• Write down all medications, including supplements and vitamins
• Take a friend or family member along. You may not always remember all the information you need to provide
• Write down the questions you want to ask your doctor

Preparing a list of questions beforehand will help you make the most of your little time with the doctor. You should consider listing the questions from the most important in case you run out of time.

Some questions you can ask the doctor are:

• What tests do I need?
• Is my condition resulting from food allergies or other reactions?
• Is my condition long-lasting or temporary?
• What are my alternatives to the primary approach you are suggesting?
• What are the available treatments, and what is your recommendation?
• How can I manage this condition with my other health condition?
• Are there dietary restrictions I should know?
• Do I need to see a specialist? How much will this cost, and will my insurance cover it?
• Are there generic alternatives to the prescribed medication?
• Do you have printed material I can take home, and what websites do you recommend?

If the visit concerns a child with a food allergy, you may also ask the following questions.

• How can I keep my child safe at school?
• Is my child likely to outgrow the allergy?
• Are there alternatives to the food that triggers my child's allergy?

What to expect from your doctor

Your doctor will likely ask several questions. Preparing to answer these questions will help save time during the appointment. These questions include:

• How severe were the symptoms?
• When did you first experience the symptoms?
• How long did it take before the symptoms occurred after eating the food you suspect triggered the allergic reaction?
• Did you take over-the-counter allergy medications like antihistamines, and if you did, did they relieve the symptoms?
• What amount of food did you eat before the reaction?
• Do you know how the food was prepared?
• Was the food that caused your allergy reaction raw or cooked?
• What seems to improve your symptoms?
• What seems to worsen your symptoms?

When to see a doctor

Ensure you see an allergist or healthcare provider if you experience food allergy symptoms shortly after you eat. If possible, visit the healthcare provider during the allergic reaction to help the provider make an accurate diagnosis.

Emergency care is necessary if you develop symptoms or signs of anaphylaxis, such as:

• Rapid pulse
• Lightheadedness or dizziness
• Constriction of the airways that make breathing difficult
• Shock with a severe drop in blood pressure

Are you experiencing any of the symptoms outlined in this article?

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Frequently asked questions

Can my GP conduct a food allergy test?

If you think you have an allergy reaction, visit your GP. If,after discussing your symptoms, your GP thinks you have an allergy, you may need a blood test called RAST test to determine the cause of your allergy. The GP may also refer you for further testing to identify the cause of your allergy.

How do you test for a food allergy in the UK?

You may need a blood test called a specific IgE test that measures the amount of IgE antibodies if the doctor suspects food in the blood. This test is a Radio Allergo Sorbent Test (RAST). Your result will help diagnoseIgE-mediated food allergy, including a detailed clinical history. Your hospital clinician or GP will conduct the test.

Which food tolerance test is most suitable?

Several food intolerance tests are available, but the most accurate food intolerance tests include the blood test for testing gluten intolerance and coeliac disease and the hydrogen breath test for diagnosing lactose intolerance.