Colds and allergies are two common conditions that affect both children and adults. While cold and allergy symptoms can be similar, they have different causes and vary in type and duration. Identifying the cause of a person’s symptoms allows for the correct treatment.

People often attribute a runny nose, headache, and watery eyes to the common cold, but these can be signs of allergies.

“Millions of Americans think they are suffering from a cold during the winter months when they’re actually experiencing allergies,” said Anju Peters, MD, Chair of the American Academy of Allergy, Asthma & Immunology (AAAAI)’s Rhinosinusitis Committee.

How can a person know the difference between an allergy and a cold?

Although symptoms are often similar, colds and allergies are different. The two conditions have different causes, and the symptoms vary in type and duration. Identifying which condition a person has allows for the most appropriate treatment.

An allergy is an overaction of the immune system to environmental exposures such as dust mites, furry pets, mold, fungi, and pollen.

The body releases compounds to combat what it perceives as a harmful substance. One of these compounds is histamine. This compound helps protect the body and fight the invader, but histamine causes many common allergy symptoms.

In essence, the immune system releases antibodies to fight something that is not actually harmful.

Allergies are very common. According to the Asthma and Allergy Foundation of America, about 50 million people in the United States have allergies. That number is much higher worldwide.

An allergy can have respiratory symptoms similar to the common cold, such as coughing, sneezing, or runny nose. However, there are also differences in symptoms.

Symptoms of an allergy

Allergies are not contagious, but the symptoms only vary slightly from the common cold, which is contagious. Symptoms include:

  • runny or stuffed nose
  • sneezing
  • wheezing
  • coughing
  • watery or itchy eyes
  • postnasal drip

The common cold is a contagious, viral illness that affects the respiratory system.

More than 200 viruses can cause a cold, and adults can expect to have two to three colds a year. Children are likely to have even more colds every year.

A person can contract a cold from touching surfaces or droplets in the air leftover from a cough or a sneeze from a person who has the infection.

The common cold can also cause symptoms such as a runny nose, a cough, or a sneeze. But it usually also causes other symptoms.

Symptoms of a common cold

A cold can often cause:

Not every person with a cold will necessarily have all of these symptoms.

Complications from a common cold

In addition to the basic common cold symptoms, a person can develop complications from a cold virus. These include:

According to Peters, “cold and allergy symptoms can be very similar, making it hard to decipher a difference between the two.

In addition to differences in symptoms, the main difference between the two is the length of time symptoms last.

A cold normally disappears after a week or so, but allergies can last much longer. In order to receive proper diagnosis and treatment, it is important to differentiate between a cold and allergies.”

A cold typically lasts for about 7 to 10 days, whereas allergy symptoms may continue as long as there is exposure to the allergen.

With allergies, symptoms may appear during a certain season or come and go based on the person’s environment. For example, if symptoms appear suddenly when a person is around animals or grass, it’s a strong sign that they are due to an allergy, not a cold.

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Infographic by Yaja’ Mulcare

Other key differences between an allergy and a cold include:

  • An allergy more often causes itchy and watery eyes.
  • A fever can occur with a severe cold, especially in children, but is not an allergy symptom.
  • A sore throat is more common with a cold.
  • Body aches do not occur with allergies but can be common with a cold.
  • Some people with allergies also develop eczema, which is not a symptom of a cold.

How to tell the difference

Asking certain questions can help someone determine whether symptoms are due to an allergy or a cold:

  • How quickly did symptoms appear? Symptoms tend to come on gradually over a day or two when a cold is the cause. When symptoms come on suddenly out of nowhere, they are more likely to be caused by an allergy.
  • How long have symptoms been present? Symptoms of a cold tend to taper off after a week or two. Allergy symptoms may last while exposure to the triggering allergen is still in the air.
  • Do symptoms occur at predictable times? If symptoms tend to occur at the same time every year, they can be due to seasonal allergies.
  • Do symptoms include itchy or watery eyes or eczema? Certain symptoms tend to occur more frequently with allergies as opposed to colds.

COVID-19 results from an infection with the virus SARS-CoV-2, so, as with a cold virus, it is not an allergy immune response.

COVID-19 also has some similarities and differences with the common cold. Both are viral illnesses, but a cold tends to cause milder symptoms. Traditionally, COVID-19 often causes symptoms such as fever, chills, loss of taste and smell, fatigue, wheezing, headache, diarrhea, and body aches.

In severe cases, a person will have difficulty breathing and may lose consciousness. An allergy may cause similar symptoms such as wheezing or shortness of breath if a person also has asthma or is experiencing anaphylaxis, which is life threatening.

However, people with severe COVID-19 may need to be hospitalized and connected to a ventilator to breathe, which is usually not the case with a cold or asthma.

It may be much more difficult to distinguish between COVID-19 and influenza, or the flu — another virus that can cause severe illness.

Learn how to tell the difference between COVID-19 and the flu.

Cold vs. Omicron variant

Many viruses that cause the common cold are different types of coronaviruses.

Recent research shows that the Omicron variant of COVID-19 may have mutated to acquire some genetic material from another cold-causing coronavirus.

This may explain, at least in part, why this strain appears to be more infectious and its symptoms appear to be milder and more similar to those of a cold.

Data from a COVID-19 symptom study, conducted by Massachusetts General Hospital, the Harvard T.H. Chan School of Public Health, King’s College London, and Stanford University School of Medicine for the health science company ZOE, showed that Omicron symptoms tend to be cold-like — mainly runny nose, headache, sore throat, and sneezing.

Omicron also appears to cause less severe illness in children under 5 years.

The symptoms of traditional COVID-19 like the Delta variant usually develop in 1–14 days, with a median period of 5 days. However, with Omicron, the median incubation period appears to be short at 3 days. The cold also usually develops in 2–3 days.

Since a person cannot know what variant of COVID-19 they may have contracted, and the symptoms may be similar, any person who experiences cold-like symptoms should have a test for COVID-19.

When to seek help?

It is not always easy to tell the difference between a cold and an allergy, so it is important to know when to see a healthcare professional. If symptoms last for more than 2 weeks or if they are severe, it may be a good idea to see a doctor.

According to the AAAAI’s referral guidelines, people who have allergies should consult an allergist/immunologist if they:

  • need to confirm the diagnosis of allergies or asthma
  • require education and guidance in techniques for self-management of allergies or asthma
  • are considering immunotherapy — allergy shots
  • have nasal polyps
  • have co-existing conditions, such as asthma or recurrent sinusitis
  • find medications to be ineffective
  • experience symptoms that interfere with quality of life or the ability to function, or both

If a person has severe symptoms such as not being able to breathe, they should seek medical attention immediately in case they are experiencing an asthma attack, anaphylaxis, or severe COVID-19.

Anaphylaxis is a severe allergic reaction that can be life threatening. The symptoms develop suddenly and include:

  • hives
  • swelling of the face or mouth
  • wheezing
  • fast, shallow breathing
  • a fast heart rate
  • clammy skin
  • anxiety or confusion
  • dizziness
  • vomiting
  • blue or white lips
  • fainting or loss of consciousness

If someone has these symptoms:

  1. Check whether they are carrying an epinephrine pen. If they are, follow the instructions on the side of the pen to use it.
  2. Dial 911 or the number of the nearest emergency department.
  3. Lay the person down from a standing position. If they have vomited, turn them onto their side.
  4. Stay with them until the emergency services arrive.

Some people may need more than one epinephrine injection. If the symptoms do not improve in 5–15 minutes, or they come back, use a second pen if the person has one.

Although some over-the-counter medications target both colds and allergies, there are several differences in treating each condition.

Treatments for a cold

Currently, there is still no cure for a cold. Treatment for a cold usually involves getting plenty of rest, staying well-hydrated, and using a humidifier to decrease congestion. Additional natural remedies can include:

  • Honey for anyone over the age of 1 year. Infants under 1 are at risk of developing botulism if they consume honey.
  • Nasal saline irrigation.
  • Using a humidifier.

However, some over-the-counter medications help improve symptoms of a cold. These include decongestants to decrease nasal stuffiness and pain medications such as ibuprofen or acetaminophen to help reduce a sore throat or body aches.

Treatments for an allergy

Doctors can identify allergy triggers through serum and skin tests. They can then develop an appropriate treatment plan.

Salt is a natural decongestant. Therefore, a person can also use natural remedies such as a saline nasal spray to try to relieve allergic symptoms, including a runny nose or congestion. Another option is a nasal saline rinse with a neti pot.

Other natural treatments that may help include:

However, a person should always try such methods in consultation with their doctor.

Prevention is also often part of a plan to treat allergies. Once the allergen has been identified, individuals should avoid it as much as possible. When avoiding an allergen is not possible, a person can treat symptoms differently from cold treatment.

People can treat allergies with the following medications:

A person can also consider immunotherapy (allergy shots) for long-term control of allergies. Allergy shots involve receiving small doses of the allergen at regular intervals over several months. The goal is to get the body used to the allergen that causes the symptoms. Over time, as the body builds up a tolerance to the allergen, symptoms often decrease.

Summary

The common cold and an allergy can have similar symptoms, so it can be hard to tell the difference between the two. However, not all the symptoms overlap.

The causes of the two conditions also differ. A cold happens due to a viral infection, while an allergy is an overreaction by the immune system to environmental exposures.

Using a saline spray can help relieve a person’s nasal congestion, whether the cause is due to a cold or an allergy. However, medical treatments for each condition are different. If a person is not sure if they have a cold or an allergy, they may want to consult a doctor for the correct diagnosis.

Since the Omicron variant of COVID-19 appears to be a milder strain and similar to a cold for many people, a person may want to have a COVID-19 test at the onset of symptoms.