Allergies themselves do not directly cause a fever. While allergic reactions can lead to uncomfortable symptoms, they do not involve a systemic elevation of body temperature. If a fever is present alongside allergy symptoms, it usually points to another underlying cause, such as an infection.
Understanding Allergy Symptoms
Allergies occur when the immune system overreacts to typically harmless substances, known as allergens, like pollen, dust mites, or pet dander. This overreaction triggers the release of chemicals, such as histamines, which cause a range of localized symptoms. Common allergy symptoms include sneezing, an itchy or runny nose with clear discharge, itchy and watery eyes, and an itchy throat. Other reactions can involve skin rashes, hives, or swelling of the face, lips, or throat.
What Causes a Fever?
A fever is defined as a temporary rise in body temperature above the normal range, which is typically around 98.6°F (37°C). A temperature of 100.4°F (38°C) or higher is considered a fever. This elevated temperature is a natural defense mechanism by the body’s immune system, which releases chemicals that reset the body’s internal thermostat to a higher level to help fight off perceived threats. Fevers are most commonly caused by infections from viruses, such as the common cold, flu, or COVID-19, or bacteria, like those causing strep throat or pneumonia. Other causes can include certain inflammatory conditions, some medications, or even heat exhaustion.
When Fever and Allergies Co-Occur
A fever can be present alongside allergy symptoms, often due to secondary infections arising from allergy-induced inflammation. For instance, prolonged nasal congestion and inflammation from allergies can create an environment where bacteria or viruses thrive, leading to secondary infections like sinusitis or ear infections. These infections can cause a low-grade fever, typically ranging from 99°F to 100.4°F (37.2°C to 38°C), or even a higher fever.
It is also common for individuals to experience allergies and a separate illness, such as a cold or the flu, simultaneously. In these cases, the fever is a symptom of the viral or bacterial infection. Sometimes, severe allergy symptoms like intense congestion, fatigue, or general malaise can make a person feel “feverish” even if their body temperature remains normal. This feeling can be mistaken for an actual fever, emphasizing the importance of measuring body temperature.
Telling the Difference and When to Seek Help
Distinguishing between allergy symptoms and an infection that causes fever involves observing specific indicators. Allergy symptoms often include itchiness in the eyes, nose, or throat, and nasal discharge is clear and watery. These symptoms tend to persist as long as exposure to the allergen continues and may recur seasonally. In contrast, fevers are accompanied by body aches, chills, and fatigue, and nasal discharge from an infection might be thicker or discolored. The onset of flu symptoms, for example, is often sudden, whereas allergy symptoms can develop more gradually.
Consult a healthcare provider if a fever is persistent, reaches 104°F (40°C) or higher, or if symptoms worsen. Seek medical attention if there is difficulty breathing, persistent chest pain, sudden dizziness, or severe muscle pain. If allergy symptoms are chronic, interfere with daily activities, or do not respond to over-the-counter allergy medications, an allergist can provide specialized diagnosis and treatment. Early consultation can help identify the underlying cause of symptoms and prevent potential complications like chronic sinus infections.