When a child experiences allergy symptoms, such as a runny nose and sneezing, the discovery of a slightly elevated temperature can confuse parents. This combination often raises questions about whether the allergic reaction itself causes the body’s temperature to rise. Understanding the distinct nature of allergic responses versus the body’s reaction to infection is important for accurately assessing the child’s condition. If both allergy symptoms and temperature elevation are present, determining the actual source of the fever is necessary.
Defining Low-Grade Fever and Allergy Symptoms
A low-grade fever is defined as a body temperature slightly above normal, but below the threshold for a full fever. While normal body temperature fluctuates, a reading between 99.6°F and 100.3°F is often considered a low-grade elevation. A true fever is recognized when the temperature reaches 100.4°F (38.0°C) or higher. This slight rise in temperature can signal a mild activation of the immune system.
Childhood allergy symptoms, often called allergic rhinitis or “hay fever,” are characterized by the body’s reaction to harmless triggers like pollen, dust mites, or pet dander. Symptoms include persistent sneezing, a clear runny nose, nasal congestion, and intense itching of the eyes, nose, or mouth. Allergies involve an immune system overreaction and the release of chemicals like histamine, which causes inflammation and irritation in the respiratory passages.
The Direct Link Between Allergies and Temperature
Allergies do not directly cause a fever. An allergic reaction is a hypersensitivity response mediated by immunoglobulin E (IgE) antibodies and the release of inflammatory chemicals, such as histamine. Fevers, in contrast, are primarily triggered by the immune system releasing pyrogens, which act on the brain to raise the body’s temperature set point in response to an infection.
The historical term “hay fever” is misleading because the condition is not caused by hay and is not associated with a rise in body temperature. While localized inflammation from severe allergic congestion might occasionally cause a minor, transient temperature elevation, this is not a true, sustained fever. If a child displays both allergy symptoms and an elevated temperature, a factor other than the allergy itself is likely responsible for the temperature increase.
Alternative Explanations for Fever
The most frequent explanation for a low-grade fever alongside allergy symptoms is a co-occurring viral illness, such as the common cold. Viral infections often produce symptoms that closely mimic allergies, including a runny nose, congestion, and coughing. Unlike allergies, viral infections activate the fever-inducing mechanisms of the immune system. This commonly causes a low-grade temperature elevation, especially in the first few days.
Allergies can also indirectly lead to a fever by creating conditions favorable for a secondary infection. Constant inflammation and congestion in the nasal passages can block the normal drainage of mucus from the sinuses. This stagnant environment can become a breeding ground for bacteria, resulting in a bacterial infection like sinusitis or an ear infection. If the temperature is accompanied by thick, colored nasal discharge or pain in the ears or face, a secondary infection should be considered.
When to Seek Medical Guidance
Parents should monitor their child closely when a low-grade fever accompanies allergy symptoms, looking for signs that warrant medical attention. A fever lasting longer than 72 hours (three days) in a child two years or older should prompt a call to a healthcare provider. Any fever that repeatedly rises above 104°F (40°C) signals a need for immediate medical evaluation.
Certain accompanying symptoms require prompt medical assessment, regardless of the temperature’s height. These warning signs include significant lethargy, unresponsiveness, difficulty breathing, a stiff neck, or a severe headache. For infants younger than three months, any temperature of 100.4°F (38.0°C) or higher should be evaluated immediately by a medical professional. Ensuring the child stays hydrated and comfortable with rest and appropriate over-the-counter fever reducers can provide supportive care.