Can Allergies Cause Fever?

You wake up sneezing, your eyes are itchy, and your nose won’t stop running—classic allergy symptoms. But then, the thermometer climbs. A fever? That’s not supposed to happen… or is it? Can Allergies Cause Fever? is a question that’s more common—and more confusing—than many realize. Before assuming it’s just a cold, there’s something worth considering. The answer might not be what you expect…

TL;DR

Allergies do not cause fever directly. If fever occurs alongside allergy symptoms, it likely indicates a secondary infection (e.g., sinusitis). Allergies trigger immune responses like sneezing, congestion, and itching, but not elevated body temperature. Chronic inflammation from allergies may weaken defenses and raise infection risk. Additionally, some conditions (colds, drug reactions, food intolerances) can mimic allergy symptoms. Accurate medical diagnosis is essential to distinguish between them.

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What’s the Link Between Allergies and Fever?

While allergy symptoms can be bothersome and at times intense, allergies on their own do not cause fever. If someone with allergies develops a fever, it’s likely due to a secondary infection, such as a sinus infection, rather than a direct effect of the allergy itself.

Allergies are immune system responses to substances known as allergens, which are normally harmless.

When a person with allergies is exposed to an allergen, the body releases histamines, which trigger symptoms like:

• Sneezing
• Nasal congestion
• Itching in the eyes, nose, or throat
• Runny nose

Fever is the body’s immune response to an infection. Allergies also activate the immune system, but in a different way, and they do not lead to an increase in body temperature. That’s why fever isn’t part of typical allergy symptoms.

Although allergies and respiratory infections can share similar symptoms, fever usually signals something else—most often an infection. Fever should not be attributed to allergies without considering other medical causes. Recognizing this difference supports accurate diagnosis and effective treatment.

Secondary Infections Associated with Allergies

Allergies don’t directly cause fever, but they can create conditions that increase the risk of secondary infections. This often happens because chronic inflammation and damage to protective barriers like the skin and mucous membranes allow pathogens to enter more easily.

While allergies don’t cause fever, they can lead to infections that do. Treating both the allergies and any complications they cause helps reduce the chance of more serious health issues.

Inflammatory Responses Similar to Fever

Fever is a common inflammatory response, but not all inflammation results in fever. Fever involves an elevated body temperature triggered by infection or systemic inflammation. In contrast, inflammation can present in other ways without affecting core body temperature.

In many cases, such as allergic reactions, the body may show localized or general signs of inflammation that resemble fever, even though the actual temperature remains normal.

Inflammatory responses that may be mistaken for fever include:

• Redness: Caused by increased blood flow to the affected area
• Swelling: Fluid buildup in inflamed tissue due to more permeable blood vessels
• Pain: Nerve endings activated in the inflamed area
• Warmth: Local increase in temperature due to blood flow
• Loss of function: Limited movement or function of the affected body part
• Fatigue: Widespread tiredness caused by chronic inflammation

While fever is a significant indicator of illness, it’s not the only one. These signs can help distinguish between active allergy symptoms and infections that require medical attention.

Fever in People with Severe Allergic Rhinitis

Severe and persistent allergic rhinitis, also known as hay fever, can produce intense symptoms. Still, fever is not a typical feature of this condition. When someone with allergic rhinitis develops a fever, it’s usually due to a secondary infection, not the allergy itself.

Even in the most severe cases, allergic rhinitis does not produce fever. Fever is a response to infection. If it occurs in someone with rhinitis, a secondary condition such as bacterial sinusitis may be responsible, especially if the nasal inflammation is ongoing.

Classification and Diagnosis

Allergic rhinitis is classified based on the frequency and duration of symptoms:

• Intermittent: Less than 4 days per week or less than 4 consecutive weeks
• Persistent: More than 4 days per week and more than 4 consecutive weeks

Management and Treatment

Effective treatment helps lower the risk of secondary infections that may cause fever. Recommended strategies include:

• Avoiding exposure to allergens
• Rinsing nasal passages with saline or seawater
• Using antihistamines to relieve most symptoms except congestion
• Applying intranasal corticosteroids to reduce inflammation

Comprehensive care can reduce the likelihood of complications, including fever-related infections.

Other Conditions Mimicking Allergy Symptoms

Several conditions can produce symptoms that resemble allergies, making diagnosis more difficult without medical evaluation. Sneezing, congestion, itching, and skin rashes are common allergy symptoms, but they don’t always point to an actual allergic reaction.

Conditions with similar symptoms include:

Other illnesses can look like allergies, which makes self-diagnosis risky. Seeing a healthcare provider helps ensure the correct cause is identified and the right treatment is given. Early evaluation and distinguishing between similar conditions can improve outcomes and avoid complications.

Key Takeaways

1. Allergies can trigger symptoms like sneezing, congestion, and itching, but not a rise in body temperature. If fever is present, it is likely due to a secondary infection, such as sinusitis.
2. Fever is a response to infection or systemic inflammation and does not occur as part of a typical allergic reaction.
3. Chronic inflammation and damage to skin or mucous membranes caused by allergies can make individuals more susceptible to bacterial, viral, or fungal infections that may cause fever.
4. Common Secondary Infections Include:
   • Skin: Impetigo, folliculitis, herpes zoster
   • Respiratory: Sinusitis, bronchitis, pneumonia
   • Fungal: Candidiasis
5. Allergies and other inflammatory conditions may cause localized redness, warmth, swelling, and fatigue—symptoms that resemble fever but without elevated body temperature.
6. Even persistent or severe allergic rhinitis (e.g., hay fever) does not produce fever. If fever is observed, a secondary bacterial infection should be considered.
7. Strategies include allergen avoidance, nasal irrigation, antihistamines, and intranasal corticosteroids, all of which help prevent complications that may lead to fever-inducing infections.
8. Conditions such as colds, drug reactions, food intolerances, dermatitis, and anaphylaxis may present symptoms similar to allergies, potentially leading to misdiagnosis.
9. Medical evaluation is critical to distinguish between true allergies and other health issues that mimic allergy symptoms or cause fever, ensuring appropriate treatment and safety.

Sources:

• Broderick, L., & Hoffman, H. M. (2020). Pediatric recurrent fever and autoinflammation from the perspective of an allergist/immunologist. Journal of Allergy and Clinical Immunology, 146(5), 960-966.
• Franjić, S. (2024). Anyone Can Have Allergies. International Journal of Medical Case Reports and Medical Research, 2(3).