Can Allergies Cause a Fever?

Dr. Menachof, MD, has specialized in conditions around the head, throat, ear, nose, neck and face for over 20 years, and was the first to bring sublingual allergy drops to Colorado in 2005. He has been recognized as a Fellow by multiple academies, named one of America’s Top Facial Plastic Surgeons continually since 2003 and is featured in multiple national publications.

Experiencing a fever with your allergies? Learn more about what causes this and how you can get your allergies treated in Denver.

The short answer is — no — allergies do not directly cause a fever. A high temperature is a sign that your body is fighting a bacterial or viral infection. Sometimes allergies can lead to a sinus infection, and a fever is a symptom of a sinus infection, so allergies can indirectly cause a fever.

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Can Allergies Cause Fever?

According to the American College of Allergy, Asthma, and Immunology, allergies do not cause a fever. However, an allergic reaction can trigger a sinus infection, eventually leading to a fever.

When your body comes into contact with an allergen, your immune system releases a chemical that shields it from the unwanted substance. This chemical — histamine — is the true culprit behind your seasonal allergy symptoms.

Common allergens include:

  • Tree pollen
  • Grass pollen
  • Animal dander
  • Ragweed
  • Dust mites
  • Mold

If you’re experiencing a fever in addition to allergy symptoms, like a runny nose or itchy eyes, it’s typically because chronic congestion in your nose has led to a sinus infection. People who suffer from allergic rhinitis are far more likely to experience chronic sinus infections, which often trigger fevers.

Common Allergy Symptoms

So, what are some strong indicators that you’re suffering from seasonal allergic rhinitis? Though it depends on the specific allergen and your body’s sensitivity, here are common ones to look out for:

Seasonal allergies aren’t the only reason for this type of reaction. Food allergies can cause some of these symptoms as well as nausea and an upset stomach. Skin rashes and hives can also indicate an allergic reaction.

What About Hay Fever?

Despite its name, hay fever, or allergic rhinitis, doesn’t actually trigger a fever. Hay fever, also known as seasonal allergies, is simply an allergic reaction to airborne irritants, like pollen and pet dander.

Just like seasonal allergies, hay fever symptoms include sneezing, nasal congestion, itchy or watery eyes, and a sore throat.


What Can Cause a Fever With Allergy Symptoms?

Many conditions can trigger congestion and other allergy-like symptoms, including sinusitis, the flu, a common cold, or COVID-19. These conditions are easily confused with seasonal allergies, so it can be difficult to determine the cause of your congestion and fever.

Here’s a breakdown of four common causes of congestion and fever.


Simply put, sinusitis is swelling in your sinuses: the hollow cavities behind your cheeks, nose, and eyes. When your sinuses become swollen, mucus builds up and blocks these passages. If you’re experiencing painful pressure behind your eyes or nose, you’re likely dealing with sinusitis.

Common symptoms of acute sinusitis include:

  • Pain in the forehead and cheeks
  • Fever
  • Stuffy nose
  • Post-nasal drip
  • Thick yellow or green discharge from the nose
  • Congestion
  • Coughing
  • Toothache


Of course, not all fevers are caused by sinusitis. The flu can trigger a fever that lasts for up to four days. Often, a case of the flu is accompanied by these symptoms:

  • Runny nose
  • Itchy nose
  • Cough
  • Sore throat
  • Headache
  • Fatigue
  • Body aches and pains
  • Low-grade fever

Common Cold

Another cause of fever is the common cold. As a viral infection, the common cold can cause fever and chills — though it’s relatively rare. Other symptoms include:

  • Muscle aches and pains
  • Headache
  • Sneezing
  • Congestion
  • Coughing
  • Low-grade fever
  • Sore throat


Like the common cold, COVID-19 is a viral illness. Different people react to COVID-19 in different ways. Fever and chills are two common symptoms of COVID-19, as well as:

  • Cough
  • Difficulty breathing
  • Fatigue
  • Headache
  • Loss of taste or smell
  • Sore throat
  • Congestion
  • Nausea or vomiting
  • Muscle aches
  • Diarrhea

If you’re still having trouble identifying the exact cause of your fever, our team at Advanced ENT & Allergy Clinic would be happy to help you. We’ll isolate the reason for your symptoms and get to work on an effective and convenient treatment strategy.

How to Diagnose Allergies

To determine whether your symptoms are due to allergies, it’s a great idea to get in touch with an ENT specialist. Once you’ve made an appointment, there are three steps that you should follow to make the most of your visit:

  • Provide a detailed personal medical history. This will help your allergist to find a connection between your symptoms and the allergens you’ve been exposed to.
  • Keep a log of your symptoms. When your symptoms appear, intensify, or disappear, make a note of it! If your allergies are seasonal, this information will be one of the keys to finding out.
  • Do an allergy test. Allergy tests are the best way to isolate the cause of your symptoms. Usually, an allergist will do a scratch test, checking your reaction to multiple allergens at once. In some cases, you might do an intradermal, skin patch, or blood test instead.

Your Treatment Options

As usual, the best treatment for you will depend on the cause of your symptoms. A bacterial or viral infection, for example, will call for a different treatment than allergies.

If a bacterial infection is the cause of your fever, a doctor will give you antibiotics, which should take effect within 1-3 days.

If a virus is behind your symptoms, your doctor might prescribe an antiviral medication — or you might have to wait the virus out. Most viruses clear up on their own within a week or two.

If you have sinusitis, a cold, the flu, or COVID-19, your doctor will encourage you to stay home, rest, and take OTC medications. Usually, you’ll start to see improvement within a week.

If allergies are the root of your symptoms, your doctor will likely recommend a combination of treatment options. We’ll walk you through some popular approaches.

Lifestyle Changes

Changing up your daily routine is an effective, low-cost way to reduce your exposure to allergens. To minimize the effect of allergies, try these ideas out:

  • Purify the air in your home.
  • Vacuum and dust regularly.
  • Take natural supplements (for example, vitamin C or peppermint oil).
  • Use nasal irrigation (including nasal sprays or a Neti pot).


Lifestyle changes are most successful when they’re coupled with medications. Medications are available over the counter (OTC) and by prescription. Usually, allergies are treated with an antihistamine like Claritin, Zyrtec, or Allegra — but other medicines can also be effective for treating allergic rhinitis.

Before you commit to a medicine, consult an allergy specialist. They’ll walk through your options and help you decide on the right one for you.

Allergen Immunotherapy

For long-term relief, allergy shots or allergy drops are the best courses of action.

Both treatments work by gradually introducing your body to specific allergens, allowing you to slowly develop tolerance to the allergen.

When to Call a Doctor

If your fever is above 104°F (40°C), contact a doctor immediately. If you have flu symptoms that last more than 10 days or if your symptoms aren’t improving with OTC medications, you should contact a doctor.

You should also see a doctor if your fever is paired with:

  • High body heat without sweat
  • Involuntary shivering or shaking
  • Hallucinations or confusion
  • Skin rashes
  • Muscle spasms
  • Increased heart rate
  • Vomiting

Seek emergency medical attention if you have an extreme allergic reaction or anaphylactic shock symptoms. Symptoms include:

  • Difficulty breathing
  • Swelling of the throat or tongue
  • Hives
  • Vomiting
  • Diarrhea
  • Loss of consciousness
  • Severe drop in blood pressure

Get Relief

Our specialists at Advanced ENT & Allergy Center will determine the root cause of your symptoms and create a treatment plan just for you. We’ll make sure that your treatment — whether it’s a lifestyle change, medication, allergy immunotherapy, or a combination of each — is effective and convenient for your daily routine.

If you’re ready to find relief from your symptoms and enjoy your next outdoor adventure, get in touch with our team today.

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Allergy + Sinus Clinic

Our team has extensive, specialized training on allergy treatment and immunology from the American Academy of Otolaryngologic Allergy. Our allergy doctors were the first doctors in the state of Colorado to treat allergies with sublingual immunotherapy. We have a 20-year track record of helping patients find lasting relief.

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