Flu vs. Allergies: What's the Difference?

Jul 14, 2022

Flu vs. Allergies: What's the Difference?

5 minute read

Everyone’s a little bit paranoid whenever they feel a sore throat looming or a couple of coughs spewing during flu season. And the threat of COVID-19 hasn’t made this fear diminish. But the next time your sinuses get congested, or your nose starts to run, it’s important not to jump to any conclusions.

While seasonal allergies share some similarities to the cold and flu, they are both very different and have their own set of symptoms. Understanding the difference might be able to save you a trip to the doctors.

Let’s answer the age-old question: what’s the difference between flu and allergies?

What Are Causes of the Flu and Allergies?

The main difference between the flu and allergies is what causes each one. Influenza, or the flu, is a contagious illness that is caused by the influenza virus.

Viruses are tiny parasites that cannot reproduce by themselves. Instead, they need to thrive off of another living being. Experts believe that viral particles are spread through small droplets in the air, contracted through inhalation.

Viruses can pose a threat to your health if your immune system cannot combat them properly, as they can kill and destroy living cells. That’s why your body forces you to cough and sneeze when you’re sick so it can try to eliminate the danger.

On the other hand, allergies are caused by allergens, any substance that makes you have an allergic reaction. The funny thing about allergens, like pollen or pet dander, is that they don’t pose any harm to your health. For some people, their immune system just wrongfully perceives them as dangerous.

When that happens, your body releases a chemical called histamine, which causes your blood vessels to expand and your skin to swell. This leads to several allergy symptoms, like sore throat, sneezing, watery eyes, and more.

On top of that, the flu virus is highly contagious and can be spread from person to person through physical contact or from droplets in the air. But you can’t give someone else your allergies. That’s good news for all your friends and family that you keep sneezing all over.

How Do Flu and Allergy Symptoms Differ?

The symptoms of allergies and the flu are often very similar, and that’s one of the main reasons it can be so hard to distinguish between the two. Symptoms usually pretty common for both the flu and colds include sore throat, sneezing, fatigue, weakness, cough, congestion or stuffy nose, or a runny nose.

However, some symptoms are specific to just one over the other. A defining symptom of the flu that should never occur with allergies is a fever of over 100 degrees Fahrenheit. Additionally, body aches, chills, shortness of breath or difficulty breathing, and extreme exhaustion (allergies can also cause exhaustion, but not as severe as the flu) are common with the flu but rarely from allergies.

Chest pains are also pretty common with the flu, and while this is rare for most individuals with allergies, it’s common if you have allergic asthma, a condition where your airways tighten when exposed to an allergen.

What Are Treatment Options for Allergies and the Flu?

Since the flu and allergies are both caused by two different things, it makes sense that their treatment methods differ as well.

Something to note about the flu is that it cannot necessarily be treated. While antiviral medications can be prescribed, the only true way to be cured of a viral infection is to allow your immune system to flush it out on its own. This can take some time, but rest assured that your body won’t let you down.

With that said, there are ways to manage the symptoms when they arise. It’s necessary to get plenty of rest and stay hydrated with plenty of fluids so that your body has the time to work its magic on the viral enemy. You can also use over-the-counter pain-relieving medications to help with some of the muscle aches and pains that are likely, and decongestants can ease a stuffy nose.

With allergies, there is actually a way to pinpoint the source and start to build up immunity so that your symptoms are less pronounced. It’s called allergy immunotherapy, and it works by gradually exposing you to your suspected allergen over time. Gradually, your immune system becomes used to the exposure, and your symptoms are less severe.

An FDA-approved form of immunotherapy called SLIT is effective, and all it takes is some dissolvable tablets under your tongue.

Did We Mention Prevention?

Perhaps the only universal similarity between the flu and allergies is that no one ever wants to deal with either. Luckily, there are some ways to avoid them.

For the flu, it’s important to wash your hands and avoid being around other individuals you know are sick from the flu. It’s also wise to wear face coverings in public, primarily until the COVID-19 pandemic fully subsides. You can also get the flu vaccine each year to help your body build immunity against influenza viral loads in the air, and also make sure you are fully vaccinated for COVID-19.

Allergies can be prevented by first understanding what’s causing them. Almost anything can be an allergen, so by taking an allergy test to fully know what you’re allergic to, you can take some preventative steps.

For environmental allergies, it’s important to wash linens often to remove pet dander and dust mites. Additionally, try to avoid going outside on dry and windy days when pollen counts are high.


Flu and allergies seem like similar ailments, but there are some key differences between the two. A virus causes the flu, and harmless allergens cause allergies. Additionally, the flu is almost always marked by a fever, but allergies should never raise your body temperature in the same way.

With that said, they both can make you feel pretty miserable. While we might not be able to help you with the flu, Cleared has everything you need to help combat the toughest allergens. Your online allergist is in.


How Infection Works - What You Need to Know About Infectious Disease | NCBI

Antihistamines | NHS UK

Cold, Flu, or Allergy? | NIH

Allergic Asthma: Causes, Symptoms, Tests & Treatment | The Cleveland Clinic


Dr. Payel Gupta

Medically reviewed by Dr. Payel Gupta



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