Can allergies cause a fever?

Key Points

• Typical symptoms of allergies include congestion, runny nose, red or watery eyes and sneezing. Allergies don’t typically cause a fever.
• Symptoms like congestion and runny nose can make you more likely to get a bacterial or viral infection. These infections could cause a fever.
• The best way to treat allergies is to avoid whatever is causing your symptoms. Other treatments include decongestants and histamine blockers.

Are allergy symptoms making you miserable? Allergies can cause a whole host of problems, from itchy, watery eyes to sneezing and congestion. But fever isn’t typically one of the symptoms of this common problem.

That said, an allergic response can lead to increased mucus production and clogged sinuses. This makes it easier for germs to grow. So people with allergies are more likely to develop an infection, which might cause a fever.

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What are allergies?

Your immune system is designed to fight invaders. Sometimes, it works a little too well. It can kick into high gear for non-threatening substances like pet dander, pollen, dust mites or certain foods.

Your body produces a substance called histamine whenever it notices a potential threat. This causes a whole cascade of reactions, including swelling and mucus production. Common treatments target histamines, which can stop that allergic response.

Common allergy symptoms

Allergy symptoms can make you pretty miserable. While the exact symptoms depend on what’s triggering your immune response, the most common allergy symptoms include:

• Itchy, watery eyes
• Congestion
• Runny nose
• Sneezing
• Post-nasal drip
• Sore throat
• Wheezing or trouble breathing
• Headache
• Sinus pain or pressure
• Skin rash

Serious allergic reactions can cause swelling in your airways and make it hard to breathe. Anaphylactic shock is a life-threatening allergic reaction that requires immediate emergency help.

Allergy symptoms with fever

Allergies can cause congestion and a runny nose. When your sinuses are full of mucus, it’s easier for bacteria or viruses to take hold. So if you have allergies, you’re more likely to get an infection.

Hay fever is the term for allergic rhinitis. Despite the name, it doesn’t actually cause a fever. (It’s also not caused by hay.) It just refers to seasonal allergies (like pollen) or environmental triggers (like cockroaches or pet dander).

If you have congestion, a runny nose and a fever, the most likely culprit is a sinus infection (or sinusitis).

What causes fever?

A typical body temperature is about 98.6 degrees Fahrenheit. But anything up to about 99.9° is still considered “normal.” A fever is anything over 100.4°.

When your body detects germs like viruses or bacteria, it launches an attack of white blood cells. As these cells fight the infection, they release a substance called pyrogens. Pyrogens raise your body temperature. This is actually a good thing—higher body temperatures mean your body is fighting viruses and bacteria so they can’t survive.

The allergic response involves a whole different immune process. This process doesn’t involve any pyrogens. No pyrogens = no fever.

Bottom line? Allergies don’t cause fevers. But infections can cause fever, especially:

• Sinusitis
• Flu
• Covid-19
• Common cold

When to see a doctor for a fever

Most of the time, there’s no need to treat low-grade fevers in adults. Remember, a fever is actually a sign that your body is doing its job. But you can take over-the-counter medicines like Ibuprofen or Acetaminophen if you’re uncomfortable.

There are a few cases when a fever needs some follow-up, though. Get help if you notice:

• Fever over 104° F
• Fever that lasts for more than three days
• Fever that doesn’t respond to medicine
• Fever plus a stiff neck, trouble breathing, dehydration or confusion
• Fever over 100.5° F in a baby
• Fever along with irritability or lethargy (acting very tired) in children
• Fever in someone with other medical conditions, like dementia, heart or lung problems or a weakened immune system

How to treat allergy symptoms

There are different ways to treat allergy symptoms. Depending on what’s causing your allergies, it may be possible to undergo allergy shots. These can help your body get used to the allergen so it doesn’t react so strongly.

There are medications that can treat allergy symptoms. Eyedrops like Azelastine and Cetirizine drops can help with itchy, red, watery eyes. Tablets like Cetirizine and Montelukast can help with symptoms like sneezing and congestion.

Are you looking for relief from symptoms like itchy eyes or sneezing? Dr. B offers same-day consultations for this common problem—for just $15. Find out how it works or get started with your online consultation today. Licensed providers are available every day of the year—weekends and holidays included!

Sources

Akhouri, S., et al. (2023). Allergic rhinitis. StatPearls Publishing.

Asthma and Allergy Foundation of America. (2015). Allergy symptoms.

Bush, L.M. (2022). Fever. Merck Manual Professional Version.

Mayo Clinic. (2023). Fever treatment: quick guide to treating a fever.