Allergies share many symptoms with sinus infections, including runny nose and itchy, watery eyes, but they can’t cause a fever. In fact, taking your temperature can help your healthcare provider determine whether you’re dealing with allergies or an infection. For adults, a fever is any temperature higher than 100.4°F. For children, a temperature of 99.5°F measured orally, 100.4°F measured rectally, or 99°F measured under the arm is considered a fever.
When you get an infection, such as bronchitis or strep throat, your immune system releases chemicals that increase your body heat and core temperature. You may also get chills, which further increase your body temperature. Then, when your core temperature resets, you start feeling warm, which can make you sweat. Most of us are familiar with this cycle of chills and sweating that accompanies colds, the flu, and other illnesses. Allergy symptoms alone cannot cause this type of reaction in your body.
Allergies don’t cause a fever
An allergic reaction happens when your body’s immune system overreacts to an everyday substance, such as pollen or pet dander. Allergens like these aren’t harmful on their own, but your body’s reaction to them can cause unpleasant symptoms. For pollen or seasonal allergies, symptoms can include itchy eyes or nose, throat swelling, fatigue, sneezing, wheezing, chest tightening, and skin irritation. They may make you feel sick and tired, but pollen or seasonal allergies cannot cause a fever or chills. Even hay fever (another term for allergic rhinitis) won’t cause an actual fever, despite its name.
Food allergies can also cause a wide range of symptoms, including hives, stomach cramps, bloating, diarrhea, and vomiting. A severe allergic reaction may even lead to a potentially life-threatening condition called anaphylaxis. However, food allergies won’t cause a fever either.
Fevers and severe illness often go hand-in-hand, but fevers themselves don’t actually pose any danger to our health. A fever is your body’s response to inflammation caused by the immune system’s response to infection or autoimmune diseases. When your body temperature rises, it helps your immune cells perform while damaging the pathogens and infected cells your body’s trying to fight.
It’s a common misconception that a high fever can harm the body or cause brain damage, especially in children, but that’s not the case. The body’s temperature will only rise that high – above 108° F (42° C) – if the air temperature is also extremely high. Otherwise, the fever itself can’t hurt you—it’s actually beneficial for fighting off an infection. The infection or autoimmune disease causing the fever is responsible for any health effects.
So, while fever-reducing medications can be used to lower body temperature and make you more comfortable when you’re sick, they won’t treat the cause of the fever or make an infection go away any faster.
Other causes of fevers
Fevers are usually caused by viral or bacterial infections, and they typically go away within a few days. However, some other conditions can cause elevated body temperature, such as heat exhaustion, autoimmune disease, inflammatory conditions, cancerous tumors, and some medications or immunizations.
Allergy symptoms can be pretty uncomfortable, and they may sometimes feel similar to cold or flu symptoms, but they won’t cause a fever. Your healthcare provider can help you determine what’s causing your fever and whether you need treatment.