Food and Drug Allergy

An immune system response to certain substances found in food or medications. The immune system mistakenly identifies these substances as harmful, leading to an allergic reaction.

A food or drug allergy occurs when the immune system mistakenly reacts to a substance that is normally harmless. Instead of tolerating the ingredient or medication, the body identifies it as a threat and launches an immune response, leading to symptoms that can range from mild discomfort to severe, life-threatening reactions. These allergies can occur in people of all ages and may develop suddenly, even if the substance was previously tolerated.

What Causes Food and Drug Allergies?

Allergic reactions happen when the immune system produces antibodies—typically Immunoglobulin E (IgE)—in response to specific foods or medications. Several factors can increase the likelihood of developing an allergy:

Genetic Tendencies

Allergies often run in families. A person with parents or siblings who have allergies is at greater risk of developing similar conditions.

Environmental Exposure

Repeated contact with allergens, early-life exposure, or environmental triggers such as pollution may increase susceptibility.

Common Food Allergens

Food allergies can involve a wide range of items, but the most common triggers include:

• Peanuts
• Tree nuts (e.g., almonds, walnuts, cashews)
• Milk
• Eggs
• Wheat
• Soy
• Fish
• Shellfish

These foods are responsible for the majority of allergic reactions, especially in children.

Common Drug Allergens

Several classes of medications can activate allergic responses:

• Antibiotics, especially penicillin and related drugs
• NSAIDs (nonsteroidal anti-inflammatory drugs), such as ibuprofen or aspirin
• Chemotherapy agents, which may cause complex immune reactions
• Monoclonal antibodies, used in certain autoimmune or cancer treatments

Symptoms of Food Allergy

Food-related allergic reactions typically develop within minutes to two hours after consumption and may include:

• Skin symptoms — hives, itching, redness
• Swelling of the lips, face, tongue, or throat
• Breathing problems, such as wheezing or tightness
• Digestive symptoms — nausea, vomiting, abdominal pain, diarrhea

Symptoms of Drug Allergy

Reactions to medications may appear quickly or after repeated exposure:

• Skin rashes or itching
• Facial swelling
• Respiratory issues, including wheezing or difficulty breathing
• Severe reactions, such as anaphylaxis

Anaphylaxis: A Medical Emergency

Both food and drug allergies can lead to anaphylaxis, a sudden and severe reaction that can involve breathing difficulty, rapid drop in blood pressure, fainting, and shock. Immediate medical attention and use of epinephrine (if available) are critical.

When to Seek Medical Care

Anyone experiencing symptoms after eating a food or taking a medication should seek evaluation from a healthcare professional. Testing, avoidance strategies, and emergency action plans—such as carrying epinephrine—can help prevent future serious reactions.