May 16, 2023/Allergies

Allergies Don’t Cause a Fever — At Least, Not Directly

Infections like sinusitis, colds, flu and COVID-19 can cause a fever, but allergies aren’t infections

person blowing their nose outside

If you have seasonal allergies, you know the drill. Wake up all congested. Headache. Puffy eyes. Gunk in your throat. Oh, the joys.

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But what’s this? A fever? Wait … can allergies cause a fever? Or is something else going on?

“Allergies don’t cause a fever. The term ‘hay fever’ is a misnomer,” explains allergy specialist Frank J. Eidelman, MD. “It’s not caused by hay and isn’t associated with a fever.”

If you’re feeling allergy-like but also spiking a fever, something else is going on. It may be that what started as allergies has left you vulnerable to a viral infection. Or maybe it’s not allergy-related at all.

Dr. Eidelman helps explain why allergies don’t cause a fever and what conditions are more likely to be raising your temperature.

Common environmental allergy symptoms

It goes by many names: allergies, hay fever, allergic rhinitis. But whatever you call them, environmental allergies are a common complaint. The U.S. Centers for Disease Control and Prevention (CDC) says that as many as 60 million people in the United States live with allergies.

A number of irritants can cause environmental allergies, like:

  • Dust mites.
  • Pollen.
  • Pet dander.
  • Mold.

Depending on what you’re allergic to, your symptoms may come and go during different seasons or stick around most (or all) the year, Dr. Eidelman says. People who are allergic to ragweed pollen, for example, experience symptoms more in the fall. People with pet or dust mite allergies tend to have symptoms throughout the year.

Common symptoms of environmental allergies include:

  • Congestion, sneezing and runny nose.
  • Itchy nose and eyes.
  • Headaches and sinus pain.
  • Sore throat from mucus dripping down their throat (postnasal drip).
  • Wheezing or coughing.
  • Trouble sleeping and fatigue.

Allergies and fevers

What’s not on the list of allergy symptoms? Fevers. Here’s why.

Fevers are a reaction to your body fighting off bacteria and viruses. When your immune system identifies an infection, it creates an army of white blood cells to fight it off. The white blood cells head off into battle. In the process, they release substances called pyrogens, which result in a fever. Essentially, a fever is your body’s way of trying to cook viruses out of your body.

Allergies, Dr. Eidelman explains, are the result of your body mounting a different kind of defense.

Environmental allergens aren’t an infection. If you have allergies, your body overreacts to allergens by releasing histamine and other chemicals that cause allergy symptoms. It doesn’t release pyrogens. No pyrogens mean no fever.

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But here’s where things get a little complicated: Allergies themselves don’t cause fevers. But, Dr. Eidelman says, “Allergies can create a predisposition to viral and bacterial infections. And those infections can, indeed, cause fevers.”

So, allergies can’t be blamed directly for that rising number on your thermometer, but they can make you more likely to get sick with other infections.

Allergies or something else?

It can be easy to shrug off infection symptoms as “just allergies.” And the opposite is true, too.

How can you tell the difference, and what can you do about it? Dr. Eidelman says fevers are one clue but there may be other signs, too:

Condition
Sinus infection
Symptoms that set an infection apart from allergies
Fever; Green or yellow mucus.
Cold
Symptoms that set an infection apart from allergies
Fever; Body aches.
Flu
Symptoms that set an infection apart from allergies
Fever; Body aches; Nausea, vomiting or diarrhea.
COVID-19
Symptoms that set an infection apart from allergies
Fever; Difficulty breathing; Body aches; Loss of taste or smell; Nausea, vomiting or diarrhea.

Sinus infection

Your sinuses are air-filled cavities that surround your nasal passageways. Normally, mucus drains out of them and down the back of your nose. But the lining of your sinuses can get irritated and swell. That results in sinusitis, or a sinus infection.

Sinus infection symptoms can be similar to allergy symptoms. But unlike allergies, sinus infections can also cause fevers and thick yellow or green mucus.

Environmental allergies can trigger sinus infections. That’s because as your body reacts to allergens, it creates extra mucus. All that mucus fills up your sinus passage. So, rather than your sinuses moving germs out of your nose, the little buggers get trapped in. Your sinus cavity then becomes a warm, moist breeding ground for germs that get you sick.

Sinus infections can be caused by either viruses or bacteria that lurk around in your sinuses. Viral sinusitis should start to resolve in five to seven days. A sinus infection that doesn’t go away after 10 days or that gets worse instead of better may be caused by bacteria. Decongestants and antibiotics usually work well on bacterial sinus infections. Visit a healthcare provider if you have sinus infection symptoms that don’t improve in a week.

Cold

The common cold is an infection caused by more than 200 different viruses. Colds usually start off with symptoms similar to allergies. That includes things like:

Those symptoms usually start off mildly for about the first three days. Then, they peak, and you may also experience some symptoms that aren’t typical of allergies. That includes things like body aches and a fever.

Cold symptoms usually start to clear up after about eight days, but your cough may remain for several weeks.

Flu

Some people think of the flu as a stomach bug, but that’s not really the case. The flu is a viral infection that can cause nausea and other tummy woes in some people. But you may have the flu and not have any stomach symptoms.

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Other symptoms of the flu may be similar to the signs of seasonal allergies, but they may also include a fever or muscle and body aches.

The flu is a viral infection that doesn’t require antibiotics. Rest, hydration and over-the-counter medications and the prescription medication Tamiflu® (oseltamivir) are the best remedies for the flu. And the flu vaccine is the best prevention.

COVID-19

COVID-19 is a potentially severe viral respiratory infection. People experience varying symptoms, but some common ones include:

  • Allergy-like symptoms.
  • Muscle and body aches.
  • Nausea, vomiting or diarrhea.
  • Loss of sense of taste or smell.
  • Fever.
  • Difficulty breathing.

People who’ve had a previous COVID-19 infection or who’ve been vaccinated against COVID-19 tend to have milder symptoms.

COVID-19 infections may be easily mistaken for the flu or a cold. The only way to know if your illness is a result of the flu or COVID-19 is by getting tested.

Treating allergies

If the reason for your sneezin’ is, indeed, allergies, what now?

“Avoiding allergens is the best way to keep your allergies at bay, but it’s not always going to be practical,” Dr. Eidelman recognizes. You probably don’t want to lock yourself in the house to avoid pollen.

Common allergy relief options include:

Talk with a healthcare provider, like a primary care provider or an allergist. They can confirm whether allergies are your issue and do an allergy test to pinpoint the exact cause(s) for your allergies. Based on that, they’ll be able to help you find your best route for relief.

Learn more about our editorial process.

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