Food allergy is an immune system reaction to a typically harmless protein found in food. This reaction can cause a range of symptoms, from mild skin irritation to severe, life-threatening anaphylaxis. While the most common type of immediate allergy usually does not cause a fever, specific, delayed food-related conditions can involve a rise in body temperature, making the relationship nuanced.
Classic Symptoms of IgE Food Allergy
The most recognized type of food allergy is the IgE-mediated allergy, involving the antibody Immunoglobulin E. When a person eats a trigger food, IgE antibodies signal immune cells to release chemicals, such as histamine. This rapid release causes symptoms that typically appear within minutes to two hours of ingestion.
Symptoms commonly affect the skin, gastrointestinal tract, and respiratory system. Skin reactions include hives and angioedema (swelling of the lips, face, or throat). Digestive symptoms include vomiting, nausea, abdominal pain, and diarrhea. Respiratory symptoms, such as wheezing or a constricted throat, are concerning. These immediate reactions do not typically include a fever, as the mechanism is an acute inflammatory response driven by histamine release.
Food-Related Conditions That Include Fever
While immediate IgE-mediated allergies do not cause fever, certain non-IgE-mediated food syndromes can. The most notable is Food Protein-Induced Enterocolitis Syndrome (FPIES), a delayed food allergy affecting the gastrointestinal tract. Unlike a classic allergy, FPIES symptoms generally occur one to four hours after the food is eaten.
FPIES reactions involve repetitive, severe vomiting and often diarrhea, leading to profound lethargy and dehydration. In severe cases, the reaction can cause changes in body temperature or lead to hypovolemic shock. Although the initial immune reaction does not generate a fever, the resulting severe dehydration can cause a temporary elevation in body temperature. FPIES is often misdiagnosed as a severe stomach infection due to the delayed onset of severe vomiting and potential temperature changes. Common triggers include cow’s milk, soy, rice, and oats, particularly in infants and young children.
When to Consult a Doctor
Any time a food causes a concerning reaction, seeking professional medical guidance is necessary. If symptoms suggest anaphylaxis—such as difficulty breathing, throat swelling, a weak pulse, or dizziness—immediate emergency care is required. For less severe but persistent food-related symptoms, consulting an allergist is the next step to determine the underlying cause.
A specialist can use diagnostic tools like skin prick tests or blood tests to measure IgE antibodies for classic food allergies. These tests are not useful for diagnosing non-IgE conditions like FPIES, which relies heavily on a detailed medical history. Diagnosis of FPIES often requires a medically supervised oral food challenge. Keeping a thorough food and symptom diary can provide the physician with important information, especially regarding the delayed nature of non-IgE reactions and any accompanying temperature spike.