Food Allergies: A Comprehensive Guide

Overview

A food allergy is an abnormal immune system reaction to certain foods. When you have a food allergy, your immune system mistakenly identifies a specific food or a substance in food as harmful. This triggers an allergic reaction, which can range from mild symptoms like hives to severe, life-threatening reactions like anaphylaxis.

Food allergies affect approximately 32 million Americans, including 5.6 million children under age 18, according to Food Allergy Research & Education (FARE). That's about 1 in 10 adults and 1 in 13 children in the U.S.

While any food can cause an allergic reaction, nine foods account for 90% of all reactions:

• Milk
• Eggs
• Peanuts
• Tree nuts (e.g., almonds, walnuts, cashews)
• Fish
• Shellfish
• Soy
• Wheat
• Sesame (added as the 9th major allergen in 2021)

Symptoms

Food allergy symptoms typically develop within a few minutes to two hours after eating the offending food. In some cases, reactions can be delayed by several hours. Symptoms can affect multiple body systems:

Skin Reactions

• Hives: Red, itchy welts that can appear anywhere on the body
• Eczema: Dry, scaly, itchy skin patches
• Swelling: Particularly of the lips, face, tongue, or throat (angioedema)
• Itching: In the mouth or skin

Gastrointestinal Symptoms

• Nausea or vomiting
• Stomach pain or cramps
• Diarrhea

Respiratory Symptoms

• Sneezing or runny nose
• Wheezing or difficulty breathing
• Coughing
• Throat tightness or hoarseness

Cardiovascular Symptoms

• Dizziness or lightheadedness
• Rapid pulse
• Drop in blood pressure
• Fainting

Anaphylaxis

This is a severe, life-threatening allergic reaction that requires immediate medical attention. Symptoms may include:

• Constriction of airways and swollen throat, making it difficult to breathe
• Shock with a severe drop in blood pressure
• Rapid pulse
• Dizziness, lightheadedness, or loss of consciousness

According to the Mayo Clinic, anaphylaxis requires an immediate injection of epinephrine (adrenaline) and a follow-up trip to the emergency room.

Causes and Risk Factors

Food allergies occur when your immune system mistakenly identifies a specific food protein as harmful. Your immune system then triggers cells to release antibodies known as immunoglobulin E (IgE) to neutralize the allergen. The next time you eat even a tiny amount of that food, IgE antibodies sense it and signal your immune system to release chemicals like histamine, which causes allergic symptoms.

Risk Factors

Several factors can increase your risk of developing a food allergy:

• Family history: You're at higher risk if asthma, eczema, hives, or allergies like hay fever are common in your family.
• Age: Food allergies are more common in children, especially toddlers and infants. As children grow, their digestive systems mature, and their bodies are less likely to absorb food or food components that trigger allergies. Fortunately, children typically outgrow allergies to milk, soy, wheat, and eggs.
• Other allergies: If you're already allergic to one food, you may be at increased risk of becoming allergic to another. Similarly, if you have other types of allergic reactions, such as hay fever or eczema, your risk of having a food allergy is higher.
• Asthma: Asthma and food allergies commonly occur together. When they do, both food allergies and asthma symptoms are more likely to be severe.

Cross-Reactivity

Some people experience allergic reactions to a food after being allergic to a different substance. This is known as cross-reactivity. For example:

• If you're allergic to ragweed pollen, you might also react to melons and bananas.
• If you're allergic to latex, you might also be allergic to bananas, chestnuts, kiwi, and avocados.

Diagnosis

Diagnosing a food allergy can be challenging. Your doctor will likely:

• Review your symptoms and medical history
• Ask detailed questions about your symptoms, including what and how much you ate, how long it took for symptoms to develop, and what symptoms you experienced
• Perform a physical exam

Diagnostic Tests

Your doctor may recommend several tests to diagnose a food allergy:

Skin Prick Test

In this test, a small amount of the suspected food is placed on your skin, usually on your forearm or back. A specialist then pricks your skin with a needle to allow a tiny amount of the substance beneath your skin surface. If you're allergic, you'll likely develop a raised bump (hive) at the test location. Results are typically available within 15-20 minutes.

Blood Test (IgE Test)

A blood test can measure your immune system's response to particular foods by checking the amount of allergy-causing antibodies (IgE antibodies) in your bloodstream. Blood is drawn in your doctor's office and sent to a lab for analysis. Results are usually available in about a week.

Oral Food Challenge

During this test, you'll eat small but increasing amounts of the suspected allergy-causing food under medical supervision. If you don't have a reaction during this test, you may not have a food allergy. This test is considered the gold standard for food allergy diagnosis but carries the risk of causing a severe reaction, so it's always conducted in a medical setting with emergency equipment and medication on hand.

Elimination Diet

You may be asked to eliminate suspected foods from your diet for a period (usually 2-6 weeks) and then reintroduce them one at a time while monitoring for symptoms. This process should always be supervised by your doctor or a dietitian.

It's essential to work with your doctor to determine the best diagnostic approach for your situation. Self-diagnosis or unsupervised testing can be dangerous.

Treatment Options

Currently, there is no cure for food allergies. The primary treatment is strict avoidance of the allergy-causing food. However, several treatments can help manage symptoms and reduce the risk of severe reactions.

Medications

• Antihistamines: These can help relieve mild symptoms like itching or hives. They should be taken as soon as symptoms appear. Examples include diphenhydramine (Benadryl) and cetirizine (Zyrtec).
• Epinephrine: This is the first-line treatment for anaphylaxis. It's available in an auto-injector (e.g., EpiPen, Auvi-Q) and should be carried at all times by those with severe food allergies. Epinephrine works by constricting blood vessels to increase blood pressure, relaxing smooth muscles in the lungs to improve breathing, stimulating the heartbeat, and stopping the release of further allergic chemicals.
• Corticosteroids: These can help reduce inflammation associated with more severe allergic reactions. They're often used in combination with other treatments for severe reactions.

Immunotherapy

Emerging treatments aim to desensitize the immune system to specific allergens. These should only be conducted under the supervision of an allergist.

• Oral Immunotherapy (OIT): Involves consuming small, gradually increasing amounts of the allergenic food under medical supervision to build tolerance.
• Sublingual Immunotherapy (SLIT): Involves placing a small amount of the allergenic food under the tongue.
• Epicutaneous Immunotherapy: Involves wearing a patch containing the allergenic food on the skin.

In January 2020, the FDA approved Palforzia, the first oral immunotherapy treatment for peanut allergies in children ages 4-17.

Lifestyle and Home Remedies

• Avoidance: Strictly avoid the allergy-causing food. Read food labels carefully and ask about ingredients when eating out.
• Wear a medical alert bracelet: This can help inform others about your allergy in case of an emergency.
• Create an emergency action plan: Work with your doctor to develop a plan outlining what to do in case of an allergic reaction.

Living with Food Allergies

Living with food allergies requires vigilance, but with the right strategies, you can manage your condition effectively and live a full, active life.

Daily Management Tips

• Read labels carefully: Always check food labels for potential allergens. Be aware that food manufacturers can change their recipes, so re-check labels even for foods you've eaten safely before.
• Be cautious when eating out: Inform restaurant staff about your allergy. Ask about ingredients and how food is prepared to avoid cross-contamination.
• Prepare for emergencies: Always carry your epinephrine auto-injector and know how to use it. Make sure family, friends, and coworkers know how to administer it as well.
• Educate others: Teach family members, friends, and caregivers about your food allergy, its symptoms, and what to do in an emergency.
• Plan ahead: When traveling or attending events, plan ahead to ensure you'll have safe food options. Consider bringing your own food if necessary.
• Join a support group: Connecting with others who have food allergies can provide emotional support and practical tips.

For Parents of Children with Food Allergies

• Inform your child's school, teachers, and caregivers about the allergy.
• Work with the school to develop a Food Allergy & Anaphylaxis Emergency Care Plan.
• Teach your child about their allergy in an age-appropriate way, including how to recognize symptoms and when to ask for help.
• Encourage your child to always carry their epinephrine auto-injector (if age-appropriate) and know how to use it.

Prevention

There's no sure way to prevent food allergies, but research has identified some strategies that may help reduce the risk, particularly in infants.

For Infants and Young Children

• Breastfeeding: The World Health Organization (WHO) recommends exclusive breastfeeding for the first six months of life. Breastfeeding may help prevent or delay the development of food allergies.
• Introducing allergenic foods early: Recent research, such as the LEAP study published in the New England Journal of Medicine, suggests that introducing peanut-containing foods to infants as early as 4-6 months of age may help prevent peanut allergies, especially in high-risk infants. Always consult your pediatrician before introducing allergenic foods.
• Avoid unnecessary delays: There's no evidence that delaying the introduction of allergenic foods beyond 4-6 months prevents food allergies.

For Everyone

• Maintain a healthy diet: A balanced diet rich in fruits, vegetables, and whole grains may support a healthy immune system.
• Manage eczema: If you or your child has eczema, work with your doctor to manage it effectively. Severe eczema may increase the risk of developing food allergies.
• Avoid smoking: Exposure to tobacco smoke may increase the risk of allergies.

Complications

Food allergies can lead to several complications, some of which can be severe or even life-threatening.

Anaphylaxis

As mentioned earlier, anaphylaxis is a severe, potentially life-threatening allergic reaction that can impair breathing, cause a dramatic drop in blood pressure, and affect your heart rate. Anaphylaxis can come on quickly and requires immediate treatment with epinephrine.

Atopic Dermatitis (Eczema)

Food allergies can cause or worsen eczema, a condition that causes skin to become inflamed, itchy, red, cracked, and rough.

Asthma

Food allergies are a known trigger for asthma symptoms in some people. In others, food allergies can cause asthma to develop.

Nutritional Deficiencies

Avoiding certain foods due to allergies can sometimes lead to nutritional deficiencies. For example, avoiding milk can lead to low calcium and vitamin D levels, increasing the risk of osteoporosis. Work with your doctor or a dietitian to ensure you're getting all the nutrients you need.

Quality of Life

Food allergies can significantly impact your quality of life, causing stress, anxiety, and social isolation. They can also lead to bullying, particularly in children.

Increased Risk of Other Allergies

Having a food allergy increases your risk of developing other types of allergic conditions, such as hay fever, asthma, and eczema.

When to Seek Emergency Care

If you've been prescribed an epinephrine auto-injector, use it immediately at the first sign of a severe reaction. Even if symptoms improve after using the auto-injector, you should still go to the emergency room for further evaluation and treatment, as symptoms can recur.

For mild allergic reactions, such as hives or itching, you can take an antihistamine and contact your doctor for further advice. However, always err on the side of caution. If you're unsure whether a reaction is severe, seek emergency care.

Remember, food allergies can be unpredictable. Even if previous reactions have been mild, the next reaction could be severe. Always be prepared and seek help when needed.