Allergies and Fever: What’s the Connection?

Allergies affect millions of people each year, often bringing symptoms like sneezing, congestion, itchy eyes, and runny noses. But when symptoms become severe, people often wonder: Can allergies cause fever? It’s a common question, especially during allergy season when other illnesses—like colds or the flu—are also circulating. In this article, we’ll explore the relationship between allergies and fever, separate fact from fiction, and help you understand when a fever might be something more than just an allergic response.

What Are Allergies?

Allergies are the immune system's exaggerated response to substances that are normally harmless. These substances—called allergens—can include pollen, dust mites, pet dander, mold spores, insect stings, certain foods, and medications. When a person is exposed to an allergen, their immune system reacts by producing antibodies that trigger the release of chemicals such as histamine. This reaction leads to classic allergy symptoms, including:

• Sneezing

• Nasal congestion or runny nose

• Itchy, watery eyes

• Skin rashes or hives

• Wheezing or shortness of breath

Despite these intense symptoms, a fever is not typically caused by allergies.

Can Allergies Cause Fever?

In most cases, the answer is no—allergies do not cause fever. A fever is usually a sign that your body is fighting an infection, such as a viral or bacterial illness. Allergic reactions are inflammatory, but they don’t produce the type of systemic immune response needed to raise your body temperature significantly.

However, things can get confusing because certain symptoms of allergies, like fatigue, sinus pressure, and nasal congestion, can feel similar to early signs of an infection. This overlap often leads people to wonder if their allergy is causing a fever.

When a Fever Happens with Allergies

While allergies themselves don’t directly cause a fever, they can contribute to conditions that result in a fever. For example:

1. Sinus Infections (Sinusitis)

One of the most common complications of untreated allergies is sinusitis. Allergic inflammation can block the sinuses, trapping mucus and creating a breeding ground for bacteria. This secondary bacterial infection can cause:

• Facial pressure or pain

• Thick, yellow or green nasal discharge

• Fatigue

• Fever

So, while the initial allergic reaction doesn’t cause a fever, the resulting infection can.

2. Ear Infections

Children with allergies are particularly prone to ear infections due to blocked eustachian tubes. Like sinus infections, ear infections may follow allergic inflammation and can present with:

• Ear pain

• Hearing difficulties

• Irritability

• Fever

3. Lowered Immune Defenses

Chronic allergies may weaken the immune system over time, making the body more susceptible to infections. A person with untreated allergic rhinitis, for instance, may experience more frequent colds or respiratory infections, where fever is a common symptom.

How to Tell the Difference: Allergies vs. Infection

Understanding the difference between allergic symptoms and a true infection is key to determining the source of a fever. Here’s how they typically compare:

If a fever is present—especially one above 100.4°F (38°C)—you’re likely dealing with an infection rather than an allergy.

Can Children Develop Fever from Allergies?

Parents often ask, "Can allergies cause fever in children?" Just like in adults, children with allergies typically do not develop a fever unless a secondary infection is present. However, children may be more vulnerable to complications from untreated allergies, such as:

• Middle ear infections

• Sinus infections

• Asthma flare-ups

If your child has persistent allergy symptoms and begins running a fever, it’s important to consult with a pediatrician to rule out other conditions.

Can Seasonal Allergies Cause Low-Grade Fever?

Some individuals report feeling warm or flushed during allergy flare-ups. This sensation is usually due to:

• Nasal inflammation

• Increased blood flow to the face

• Dehydration

While these symptoms may mimic the feeling of a mild fever, they rarely involve an actual temperature increase. Taking your temperature with a thermometer can help determine if you truly have a fever.

What About Food Allergies?

Food allergies are caused by the immune system's reaction to certain proteins found in food. Symptoms can be mild or severe and typically appear within minutes to hours after eating. These may include:

• Skin reactions like hives

• Swelling of the face, lips, or throat

• Digestive issues (nausea, vomiting)

• Anaphylaxis (a life-threatening reaction)

Fever is not a recognized symptom of food allergies. If you or someone else develops a fever after eating, it's more likely due to foodborne illness (such as food poisoning) than an allergic reaction.

When to Seek Medical Help

If you’re experiencing allergy symptoms with a fever, it's important to consider other possibilities. Seek medical attention if:

• Your fever is 101°F (38.3°C) or higher

• You have severe sinus or facial pain

• Your symptoms last longer than 10 days

• Your child seems very lethargic or irritable

• You have trouble breathing or chest tightness

Early treatment of secondary infections or other illnesses is essential for preventing complications.

Managing Allergies to Prevent Complications

Managing your allergies effectively can help you avoid sinus infections and other problems that may lead to fever. Consider the following tips:

1. Avoid known allergens: Use air purifiers, stay indoors during high pollen times, and keep your home clean and dust-free.

2. Use over-the-counter treatments: Antihistamines and nasal sprays can help control inflammation and mucus production.

3. Rinse nasal passages: Saline sprays or neti pots can help flush out allergens and reduce sinus blockage.

4. Consider allergy testing: Identifying your specific triggers can help you take targeted steps to avoid flare-ups.

5. Talk to an allergist: Immunotherapy (allergy shots or tablets) can offer long-term relief and reduce the need for medication.

Final Thoughts

So, can allergies cause fever? The answer is: Not directly. Allergies are not infections, and therefore they don't typically result in elevated body temperatures. However, allergies can lead to complications—such as sinus or ear infections—that do cause fever.

By understanding the difference between allergy symptoms and signs of infection, you can take the appropriate steps to manage your health. If you're unsure whether your symptoms are due to allergies, infection, or both, a healthcare provider can help you get a clear diagnosis and proper treatment.