Allergies vs. common colds: What’s the difference?

Waking up sneezing and coughing isn’t exactly a great start to the day. But how can someone tell if it’s allergies or the beginning of a common cold? This guide breaks down a few differences between the two conditions, so people can feel confident that they can manage symptoms when they strike.

In this article:

What are allergies and what is the common cold?

Both allergies and the common cold can affect the respiratory system, which includes the body parts that help people breathe, like the nose, throat and lungs.

Allergies happen when the immune system deems a substance to be harmful and overreacts to it. The substances that can cause an allergic reaction are called allergens and can cause symptoms like sneezing, itchy eyes and congestion. A few examples of potential allergens are pollen, dust or pet dander. In 2021, more than a quarter of people in the U.S. reported having a seasonal allergy, eczema or a food allergy. (Eczema is a genetically increased predisposition to having an allergic skin response to various environmental triggers.)

Common colds, on the other hand, are viral infections that most often affect the upper respiratory tract, which includes the nose, mouth and throat. Adults in the U.S. catch two to three common colds each year on average, while kids typically catch even more.

What can cause allergies and common colds?

Allergies can happen when the body overreacts to certain triggers, called allergens. Some common allergies include:

• Food allergies (e.g., peanuts, milk, eggs, shellfish)
• Environmental allergies (e.g., pollen, mold, pets, dust mites)

Common colds are caused by over 200 different viruses. Some of the most common include:

• Rhinoviruses (most frequent cause of common colds in the U.S.)
• Human coronaviruses (these are not the same as SARS-CoV-2, also known as COVID-19)
• Parainfluenza viruses
• Adenoviruses
• Enteroviruses (including EV-D68)
• Human metapneumovirus

Can allergies and common colds spread?

Allergies aren’t contagious, so they’re not going to spread from person to person like the common cold or the flu. The way someone experiences allergy symptoms is by touching, eating or inhaling something they're allergic to.

People can catch common colds several ways:

• Being near someone who sneezes, coughs or blows their nose
• Close personal contact (e.g., shaking hands with an infected person and then touching eyes, nose or mouth)
• Touching their eyes, nose or mouth after touching a contaminated surface (e.g., doorknob, phone or shared object that the virus is on)

People with a common cold are most contagious in the first two to three days after symptoms start. They are less contagious after a week.

When do seasonal allergies and common colds happen?

In many areas of the U.S., spring allergies — often caused by grass or tree pollen — begin in February and last through the early summer. Fall allergies are often triggered by ragweed, which blooms and releases pollen from August to November. In many areas of the country, ragweed pollen levels are highest in early to mid-September.

Common colds, on the other hand, can occur year-round but are most common during the winter or rainy seasons.

How long do allergy and common cold symptoms last?

• Allergies can last for as long as someone is exposed to the allergen. This is often for up to several weeks during pollen seasons in spring, summer or fall.
• Common colds usually last less than a week.

What happens if allergies or common colds go untreated?

Allergies

When allergies are left untreated, they may result in:

• Sinus infections. Allergies can irritate the sinuses, causing them to get blocked and filled with fluid. This may cause pressure and pain in the face, a stuffy nose and other symptoms.
• Ear infections. Allergies can cause swelling and fluid that block the eustachian tube. (The eustachian tube connects the middle ears to the back of the throat.)
• Worsened asthma. Allergens can make the airways in the lungs swell up, which makes it harder to breathe. This can lead to an asthma flare-up or attack.
• Increased risk of mouth breathing. Allergies can cause congestion in the nose, causing people to breathe through their mouth more. Mouth breathing can lead to bad breath and dry mouth. It can also leave people feeling more tired than usual.

Common colds

Common colds may occasionally linger and can result in:

Mild to moderate complications:

• Middle ear infections (infection behind the ear drum)
• Sinus infections

Potentially severe complications:

• Asthma attacks (wheezing, difficulty breathing)
• Bronchiolitis (infection of the small airways)
• Bronchitis (infection of the large airways)
• Pneumonia (infection of the lungs)
• Worsening of chronic medical conditions (for example, chronic obstructive pulmonary disease, heart failure)

Management of allergies and common colds

Allergies

Effective allergy symptom relief support depends on a person’s medical history, test results and symptom severity. A management plan may include one or more of the following:

• Avoiding allergens
  • Removing the source of allergens from the home and other places someone spend time at
  • Washing out the nose daily with nasal saline rinses 
• Medications
  • Antihistamines
  • Corticosteroid creams or ointments
  • Decongestants
  • Mast cell stabilizers (these come in both OTC and prescription medications)
  • Nasal corticosteroids
  • Oral corticosteroids (if recommended and prescribed by a health care provider)
• Immunotherapy
  • When allergies are resistant to standard medications, immunotherapy can be considered. When recommended by a health care provider, this treatment option may help some people become less sensitive to allergens.

People should visit a health care provider if symptoms last beyond 10 days without getting better, if they have trouble breathing, if they are dehydrated or if they have a fever lasting longer than 4 days.

Common colds

Most people get over a common cold on their own without needing to see a health care provider.

Before taking any OTC symptom relief support medication, it’s important that people check in with a health care provider or pharmacist. Health care providers can help patients understand how to use the medication properly and make sure it won’t conflict with any other medications they’re taking. If people take medication, they should follow the directions on the package.

Some different ways to help ease symptoms and start feeling better include:

• Getting plenty of rest
• Drinking lots of fluids
• Using a clean humidifier or cool mist vaporizer
• Using saline nasal spray
• Breathing in steam from a bowl of hot water or a warm shower
• Using throat lozenges or cough drops
• Honey (or corn syrup) to help thin mucus and loosens the cough (only for us in those 1 year and older)
• Taking OTC medicines (e.g., pain relievers and fever reducers)

For kids, caregivers can do the following:

• Use a rubber suction bulb to help clear mucus from a young child’s nose
• Sit with a young child in a steamy bathroom
• Have the child take acetaminophen or ibuprofen to help reduce fever

Ways to help prevent allergies and common colds

Allergies

• Avoiding allergens when possible
• Keeping a diary to track symptoms and triggers
• Taking prescribed allergy medicines

To help prevent allergies, it is best to use all methods together.

Common colds

• Avoiding touching the face with unwashed hands
• Cleaning frequently touched surfaces like doorknobs and phones
• Getting enough sleep, eating well and exercising to help support the immune system
• Staying home when sick to avoid spreading the virus
• Using alcohol-based hand sanitizer when soap and water aren’t available
• Washing hands often, especially before eating or after using the bathroom

To help prevent common colds, it is best to use all methods together.

How allergies and common colds are diagnosed

Allergies

Health care providers may use three main methods to diagnose allergies:

1. Personal and medical history. A health care provider will ask the patient questions to get a complete understanding of the symptoms and their possible causes.
2. Physical exam. If a health care provider thinks someone has an allergy, they will pay close attention to the patient’s ears, eyes, nose, throat, chest and skin during the exam. This exam may include a lung function test to detect how well people exhale air from their lungs. They may also need an X-ray of the patient’s lungs or sinuses.
3. Allergy tests. A health care provider may do a skin test, patch test or blood test. No one test alone can diagnose an allergy. Test results are just one of many tools available to assist a health care provider in making a diagnosis.

Common colds

No special tests are needed to diagnose a common cold. In most cases, people can recognize the symptoms on their own. If they do visit a health care provider, diagnosis typically involves a simple physical exam and a review of symptoms.

Key takeaways

Allergies and the common cold can feel similar, with overlapping symptoms like sneezing, coughing and a runny nose. But their causes are different. Allergies result from the immune system’s reaction to allergens and aren’t contagious. Common colds, meanwhile, are contagious and caused by viruses.

Allergy symptoms can linger, especially if people aren’t able to avoid a specific trigger. Common cold symptoms typically clear up within one week. Lingering allergies or common colds can potentially lead to infections like sinus or ear issues, worsen asthma and in severe cases, cause bronchitis or pneumonia. OTC medications can help relieve symptoms of both. However, it’s important to choose the right management options for the underlying cause. People should always consult a health care provider before starting any new medication.