What is the Difference Between Cold, Flu, and an Allergy?

man with cold

The Centers for Disease Control (CDC) informs us that adults get an average of 2-3 colds per year, and 24-47 million people have suffered from influenza this past season. And that’s without adding allergies to the mix! Continue reading to learn more about the difference between a cold, the flu, and allergies!

Do You Have a Cold, the Flu, or Allergies?

When you’re suffering from a sore throat so raw you can’t swallow, the last thing on your mind is the need to define what’s causing your symptoms. However, it’s crucial to distinguish between a cold, the flu, and allergies. Knowing what you have can help you tailor your treatment plan to get the most out of it and feel better sooner.

Colds vs. Allergies: How to Tell the Difference

It can be challenging to tell the difference between a cold and an allergy, as both can present similar symptoms. To make matters worse, many people suffer from both simultaneously! The key to distinguishing between the two is understanding their different causes. 


The common cold is caused by viruses that enter your nose or mouth and spread throughout your body, such as rhinoviruses, parainfluenza, or seasonal coronaviruses. 

This type of infection is super contagious and typically lasts up to two weeks. Before moving on, let’s give a quick primer on how viruses work and how our body responds to them.

How Viruses Cause Sickness

Viruses may sound complicated, but they’re actually quite simple. These microbes are like tiny pieces of code that can enter your body (uninvited) and make you sick. Once they’re done with you, these microscopic invaders jump from person to person through the air, physical contact, or even food and water. 

When a virus enters your body, it interacts with your cells and replicates itself quickly. This causes an immune response in which your body recruits white blood cells to fight off the virus. 

Unfortunately, this often leads to symptoms such as fever, aches, exhaustion, or sneezing — all signs of you getting sick! The tricky part about viruses is that they’re constantly evolving, so it can be challenging for your body to fight them off. 

That’s why taking precautions like washing your hands often and getting vaccinated against certain viruses is important. Now that that’s out of the way let’s look at some of the symptoms created when our body fights these pesky invaders.

Common signs and symptoms of a cold include:

  • Congestion and sneezing 
  • Runny nose 
  • Coughing 
  • Sore throat 
  • Headache and body aches 
  • Low-grade fever (below 100.4°F) 

It can be easy to confuse the runny nose and congestion of a cold for allergies, but some key differences can help you differentiate between the two. 


Unlike colds and flu, allergies are not caused by viruses or bacteria. They are triggered when your body overreacts to a harmless substance that it mistakes for a threat – such as pollen, dust mites, pet dander, or certain foods. 

Allergies can also be seasonal or cause year-round symptoms depending on the allergen in question. When your body’s immune system mistakes harmless allergens such as pollen or dust for harmful invaders, an allergic reaction is created. 

Here’s a short description of the body’s immune response and why it causes allergies.

The Allergic Response

When we come into contact with an allergen, our immune system kicks into gear. It’s like it sounds the alarm and sends out soldiers to fight off a foreign invader. These “soldiers” are antibodies that attach themselves to the allergen to neutralize them. 

In response, our body releases chemicals such as histamine, which causes inflammation in order to protect us from this perceived threat. This is why people who suffer from allergies often experience symptoms such as congestion, sneezing, watery eyes, and hives – they’re simply signs of your body’s reaction to the allergen.

These allergies are not contagious like a cold but can last for days or weeks if not correctly managed. Symptoms shared by most allergy sufferers include:

  • Itchy and watery eyes 
  • Nasal congestion, sneezing, or a runny nose 
  • Coughing 
  • Wheezing 
  • Skin rash or hives
  • Itchy palate (the roof of your mouth) and ears

Sadly, these responses can last up to several weeks or more depending on exposure levels and other factors. While most seasonal allergies are annoying (we get it, sometimes really annoying), they can progress into something more severe. If allergies are left untreated, they can lead to asthma attacks or even pneumonia.

Similarly, a sinus infection or an ear infection may develop if the allergic reaction isn’t taken seriously and is left untreated. Allergic rhinitis can also cause swelling in the airways of your nose, which can result in difficulty breathing. 

It’s important to take any allergy symptoms seriously and consult with your doctor immediately so that you don’t end up with a more serious medical condition. 

Now that we’ve compared cold and allergy symptoms, let’s move on to the differences between cold and flu.

What is the Difference Between a Cold and Flu? 

It’s easy to confuse cold and flu since they both cause respiratory illnesses. We know they are similar in that they can both make you feel miserable, but a few key differences help us tell them apart. 

Flu is caused only by influenza viruses, while many different viruses can cause the common cold. People with colds may experience runny or stuffy noses more often than those with flu. 

Although both illnesses can make you feel tired, those with flu tend to suffer from much worse symptoms like fever or chills, body aches, and headaches. 

Thankfully, colds usually don’t lead to serious health issues like pneumonia, unlike the flu. So if you’re feeling a bit under the weather, knowing the difference between a cold and the flu can help you figure out how best to take care of yourself.

The following are some of the symptoms most associated with the flu to help you recognize it if you contract it (hopefully, you won’t)!

  • Fever 
  • Chills 
  • Coughing 
  • Sore throat 
  • Runny or stuffy nose 
  • Muscle aches and pains 
  • Extreme fatigue 

The flu is not to be taken lightly since between 16,000 to 48,000 people have died from it this season alone in the US. Possible severe complications to be wary of with the flu are:

  • Pneumonia 
  • Worsening of chronic medical conditions such as asthma, congestive heart failure, or diabetes 
  • Dehydration

Now that you’re thoroughly confused, let’s make it easier to compare the symptoms of colds, flu and allergies by putting them in a handy chart.

Chart Comparing Cold, Flu, and Allergy Symptoms

FeverRareHigh (102-104°F)Last 3-4 daysAbsent
Aches, PainsUsual but slightOften severeNever
Fatigue, WeaknessQuite mildCan last up to 2-3 weeksCommon
Extreme ExhaustionNeverEarly and prominentUnusual
Stuffy NoseCommonSometimesCommon
Sore ThroatCommonSometimesCommon
Chest Discomfort, CoughMild to moderate hacking coughCommon, can become severeSometimes
Skin Rash or HivesSometimes, can be caused by virusSometimes, can be caused by virusCommon
ComplicationsSinus congestion or earachePneumonia, can be life-threateningAsthma, ear infection, sinusitis, bronchitis, nasal polyps
PreventionNoneAnnual flu vaccine, antiviral drugsControlling the environment
TreatmentOnly temporary relief of symptomsAntiviral drugs 24-48 hrs after the onset of symptomsControlling the environment, medication, allergy injections
Occurrence3-4 times yearlyOnce yearlySeasonally, repeatedly

Stay Safe this Cold, Flu, and Allergy Season!

Cold, flu, and allergy season can be a difficult time of year for many people. Understanding the differences between these three illnesses is essential so you can take steps to protect yourself and your loved ones. 

Colds are caused by viruses, while influenza viruses cause flu. Allergies are triggered when your body’s immune system reacts to environmental allergens, such as pollen or dust mites. 

If you do end up with a cold or flu this season, there are some things that you can do to help keep yourself healthy: get plenty of rest; drink lots of fluids; practice good hygiene like washing your hands often; and take over-the-counter medication as recommended. 

If you have an allergy, talk to your doctor about the best treatment options for you. By understanding the differences between colds, flu, and allergies and taking steps to protect yourself, you can stay safe this season! However, if you’re ever unsure of what is causing your symptoms or how to treat them, it’s always a good idea to contact a doctor or healthcare provider.

Leave a Reply