Fever is generally not a direct symptom of allergies. While allergic reactions involve the immune system, they manifest differently than the body’s response to an infection that causes a fever. Allergic responses are usually localized reactions to specific triggers rather than systemic elevations in body temperature.
The Nature of Allergic Reactions
Allergies occur when the immune system mistakenly identifies a harmless substance, such as pollen, dust mites, or certain foods, as a threat. The body releases chemicals like histamine from mast cells, which are immune cells found in tissues throughout the body.
The release of histamine and other inflammatory mediators leads to the characteristic symptoms of an allergic reaction. These often include sneezing, a runny nose, nasal congestion, and itchy, watery eyes. Skin reactions like hives, which are itchy red welts, or eczema can also manifest. In more severe cases, individuals might experience shortness of breath or wheezing. These symptoms are localized to the area of allergen exposure or manifest as a widespread rash, but they do not cause a systemic increase in body temperature.
What Causes a Fever
A fever represents the body’s natural defense mechanism, signaling that the immune system is actively combating a perceived threat. It occurs when the hypothalamus, a region in the brain that regulates body temperature, raises the body’s set point in response to substances called pyrogens.
Conditions that cause fever include viral infections, such as the common cold, influenza, or mononucleosis. Bacterial infections like strep throat, pneumonia, or urinary tract infections also frequently lead to an elevated body temperature. A fever is primarily a sign of infection or systemic inflammation, indicating the body is working to eliminate an invading microorganism.
Differentiating Symptoms and Seeking Guidance
Distinguishing between allergy symptoms and those of an illness that causes fever involves observing accompanying signs. Illnesses like the flu or a common cold frequently present with systemic symptoms such as body aches, chills, fatigue, and a general feeling of being unwell, often alongside respiratory symptoms. These systemic indicators are generally absent in allergic reactions, which tend to be more localized and lack the overall malaise associated with infections.
If a fever persists for more than a day or two, or if symptoms worsen significantly, seeking medical advice is appropriate. Consulting a healthcare professional is also advisable if there is uncertainty about the underlying cause of symptoms, especially when experiencing severe breathing difficulties, persistent coughing, or unexplained rashes.