Allergies represent an immune system reaction to substances that are typically harmless to most individuals. These substances, known as allergens, can include pollen, dust mites, pet dander, certain foods, or insect venom. When an allergic person encounters an allergen, their immune system mistakenly identifies it as a threat, triggering a response that causes various symptoms. Common allergic reactions often involve sneezing, a runny or stuffy nose, itchy eyes, skin rashes or hives, and a cough.
Allergies and Body Temperature
Allergies do not cause an elevation in core body temperature, despite the misleading term “hay fever,” which is not associated with a rise in body temperature. Allergic reactions involve an inflammatory response, releasing chemicals like histamine, which differs from the physiological mechanism that induces a fever.
A fever is typically a sign that the body is fighting off an infection, such as a virus or bacteria, by increasing its internal temperature. The immune system releases substances called pyrogens in response to these pathogens, signaling the brain to raise the body’s thermostat. Unlike infections, allergies do not involve pathogens, so they do not trigger pyrogen release or a fever response. Feeling unwell or fatigued due to allergy symptoms, like congestion or headache, can sometimes be mistaken for a fever, but it does not indicate an actual increase in body temperature.
Spotting the Difference
Distinguishing between allergy symptoms and those of an infection, such as a cold or the flu, is important for appropriate self-care. Allergies often present with intense itchiness of the eyes, nose, or throat. Nasal discharge is typically clear and watery, and sneezing can be frequent. These symptoms tend to persist as long as allergen exposure continues, potentially lasting for weeks or months during peak allergy seasons.
In contrast, a common cold usually develops gradually. While it shares symptoms like a runny nose, congestion, and cough, itching is absent. Cold symptoms typically resolve within seven to ten days, and any fever is usually low-grade. The flu often has a sudden onset with more severe symptoms, including a high fever, body aches, chills, and fatigue. Nasal discharge with a cold or flu can become thicker and discolored, and a sore throat is also common.
Allergies can sometimes create an environment conducive to secondary infections, particularly sinus infections, due to inflammation and mucus buildup. If a fever develops alongside allergy-like symptoms, it is more likely due to a secondary infection rather than the allergy itself. While allergies do not cause fever, their complications can.
When to Seek Medical Advice
Consulting a healthcare professional is advisable if a fever accompanies allergy-like symptoms, as this often indicates an underlying infection. Seek immediate medical attention if an adult’s fever reaches 103 degrees Fahrenheit (39.4 degrees Celsius) or higher. A persistent fever lasting more than three days, despite self-care measures, also warrants medical evaluation.
Certain accompanying symptoms with a fever signal a need for prompt medical attention. These include:
- Severe headache
- A stiff neck
- Unusual sensitivity to light
- Difficulty breathing or chest pain
- Confusion
- A rash that does not blanch when pressed
- Severe abdominal pain
- Persistent vomiting
- Seizures
For infants and young children, specific fever thresholds and behavioral changes, such as extreme irritability or sluggishness, necessitate immediate consultation with a healthcare provider. A medical professional can accurately diagnose the cause of symptoms and recommend the appropriate course of treatment.