Can food allergies cause fever?

The vast majority of common food allergies will not directly cause fever, but a small number of severe allergies, or allergies accompanied by mucosal damage and secondary infection, may indeed show an increase in body temperature. There is still some clinical controversy over whether fever is a direct symptom of food allergy.

In the past few years in the allergology department, I have encountered many patients who treated low-grade fever caused by allergies as colds. The one who impressed me most was a boy who had just entered elementary school. He developed urticaria and frequent vomiting the same day he ate deep-sea cod for the first time. His fever reached 38°C in the middle of the night. His parents gave him cold medicine. It was of no use. I came for a blood test the next day and found that the viral and bacterial infection indicators were all normal, except that the eosinophils were three times higher than the normal value. I prescribed oral anti-allergic drugs and asked the parents to stop all suspected allergenic foods. In the afternoon of the same day, the child's body temperature returned to normal, and most of the rash disappeared.

Many colleagues believe that the nature of fever in this type of situation is a complication of allergy, not a direct result of the allergy itself - either the allergy causes frequent diarrhea and vomiting, and the body experiences stress-induced low fever, or the skin and intestinal mucosal barriers are damaged during the allergy, and a small amount of bacteria in the environment causes a minor infection, which causes the body temperature to rise.； However, in recent years, new studies have come to different conclusions: During a severe immediate allergy attack, the immune system is overactivated, and a large amount of inflammatory factors released will directly affect the temperature regulation center of the hypothalamus. Even if there is no co-infection, a transient low fever may occur, which is equivalent to the immune system "firing too hard" after recognizing the wrong enemy, and even the "command" that controls body temperature is affected.

In fact, no matter how it is discussed academically, the logic for ordinary people to deal with this kind of situation is very similar: if after eating food that has not been eaten before or is clearly suspected of allergenic food, the typical allergic symptoms of rash, itching, vomiting and diarrhea, and throat tightness first appear, and then a low fever below 38.5°C occurs, and there are no cold symptoms such as sneezing, sore throat, and cough, the priority is related to food allergy.； If your body temperature exceeds 38.5°C and persists, or you have difficulty breathing or large areas of swelling throughout your body, don’t hesitate to go to the emergency room to avoid a more serious allergic reaction.