Can Allergies Cause a Fever?

If you suffer from allergies, including allergic rhinitis, or hay fever, you are already aware of how miserable the symptoms of an allergy attack can be.

However, sometimes allergy attacks last for several days or longer, and your symptoms can start to look a lot more ambiguous. It’s easy to start to wonder if you might actually be coming down with something instead.

The symptoms of the cold, flu, and an allergy attack often overlap, which can make it difficult to know whether you need to take another antihistamine or visit your doctor.

One of the biggest differentiators between the three illnesses is the prevalence of fever. Can allergies cause a fever?

What Causes Allergies?

When people say that they have allergies or are suffering from an allergy attack, most are referring to allergic rhinitis, also called hay fever.

Allergies to things like foods, insect bites, and medications cause a different type of allergic reaction, often marked by hives, swelling, a skin rash, and anaphylaxis.

Allergic rhinitis causes cold-like symptoms including a runny nose, watery or itchy eyes, nasal congestion, sinus pressure, itchy nose, cough, postnasal drip, wheezing, fatigue, and sneezing.

Allergic rhinitis is typically triggered by environmental factors, many of which are airborne.

Some, like dust mites, pet dander, and cockroaches can be present year-round, while others are seasonal and affect allergy sufferers only at certain times of the year. Common allergic rhinitis triggers include:

  • Tree pollen (common in early spring)
  • Ragweed pollen (common in fall)
  • Grass pollen (common in late spring and summer)
  • Dust mites, pet dander, and cockroaches (common year-round, but can be worse in the winter with reduced air circulation indoors)
  • Fungi and mold spores (seasonal and perennial depending on whether they are indoors or outdoors)

Can Allergies Cause a Fever?

Although allergic rhinitis and seasonal allergies are often called “hay fever,” the name is actually a misnomer.  

According to the National Institutes of Health, airborne seasonal allergies are never associated with a fever, so allergies cannot cause a fever.  

Allergies can cause many other uncomfortable symptoms that might seem like a virus, including:

  • Fatigue or weakness
  • Runny or stuffy nose
  • Sneezing
  • Sore throat
  • Cough
  • Headache 

However, unlike viral illnesses like the cold and flu, there are some symptoms that allergic rhinitis never causes, including:

  • Fever
  • Body aches and muscle pains
  • Extreme exhaustion

There are some cases in which allergies can eventually contribute to the development of a sinus infection.

Allergic rhinitis causes the production of excess mucus, and the mucus and other debris can get trapped in the sinus passages.

A virus or bacteria can then cause a sinus infection in the existing mucus that was produced by allergies.

However, allergies themselves do not cause the infection, they simply provide an opportunity for infection by viruses or bacteria that are already present. 

How Do I Know What Is Making Me Sick?

It can be difficult to tell the difference between symptoms and conclusively determine on your own whether you’re dealing with a bad allergy attack, the cold, or the flu. However, fever is one of the major differentiators between the three conditions.

Fever is never associated with allergies, so if you have a fever, you can be certain that your symptoms are being caused by some type of infection rather than airborne allergies.

The temperature of the fever is also important, as colds can sometimes cause a low-grade fever (below 100 degrees Fahrenheit) and flu typically causes a high fever (100 to 102 degrees or higher) that can last between three and four days.

Headache is also a common symptom of the flu that is uncommon for both colds and allergic rhinitis.

On the other hand, sore throats are very common for colds but are much less common for the flu and allergic rhinitis, so a sore throat is often a sign of a cold. Allergic rhinitis often causes itchy, watery eyes, while colds and flu do not.

Regardless of what you think might be causing your symptoms, if you notice your symptoms worsening or extending for a long period of time, it is recommended that you call your doctor to discuss your condition.

Symptoms of the common cold last up to two weeks, while symptoms of the flu last one to two weeks, and allergic rhinitis can linger as long as the allergens are present.

How Can I Prevent an Allergy Attack?

Allergic rhinitis may not cause a fever, but it can still leave you feeling pretty miserable.

To avoid an allergy attack, it’s recommended that patients first try to identify what they are allergic to and then take the following steps to reduce allergy symptoms:

  • Limit time spent outdoors during times when counts of pollen, ragweed, or mold are very high. Many weather mobile apps have the option to look at pollen counts on a daily basis, and the National Allergy Bureau also offers an online tool that can help you determine the best days to spend outdoors. 
  • When allergen counts are high, keep the windows in your home closed and use air conditioning to avoid allowing airborne allergens into your home.
  • Avoid yard work, including raking leaves, working in the garden, or mowing the lawn when allergen counts are high. If you absolutely must work outdoors during allergy season, wear a mask to reduce the likelihood of breathing in airborne allergens.
  • Change your clothes and wash your hands after going outside or petting animals.
  • Consider taking an over the counter medication to reduce your allergy symptoms. Both decongestants and antihistamines are available, some of which are meant to act quickly when you’re suffering from symptoms and others that are designed to prevent symptoms. If you choose to take a maintenance or preventative medication like Zyrtec or Claritin, start taking your medication at least two weeks prior to the start of allergy season. 
  • Some people may need to take a stronger medication to control their allergy symptoms or may need to receive allergy shots. If your allergy symptoms are persistent after trying all of the above, talk to your doctor about your allergies.

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medically reviewed and fact checked