If you have a runny nose, sore throat, and headache, it could be a cold. Or it could be seasonal allergies.
Knowing which you are dealing with will help you choose the most appropriate treatments and, in turn, best alleviate your symptoms.
To help you find relief, this article will explore the differences between allergies and the common cold. I will address the symptoms, causes, timing, diagnosis, and treatments for each.
I’ll also explain how contagious each is and when to see a healthcare provider for help.
However, there are some distinct differences that may help you figure out which one you have.
Seasonal allergies (a.k.a. hay fever) may cause one symptom or many.
Symptoms may also come and go depending on how much you are exposed to the allergy trigger.
Common seasonal allergy symptoms include:
- Itchy or watery eyes
- Sore throat
- Postnasal drip
- Mild headache
- Low-grade fever (with severe allergies)
The common cold is caused by many different viruses that tend to cause the same set of symptoms.
Common cold symptoms include:
- Mild body aches
- Low-grade fever
- General feeling of unwellness
- Runny nose or congestion
- Yellow or green nasal discharge
- Sore throat
- Hoarse voice
The main differences between allergies and colds are that seasonal allergies:
- Rarely cause fevers
- Rarely cause coughing or hoarseness
- Do not cause yellow or green nasal discharge
- Do not cause body aches
It is also possible to have both seasonal allergies and a cold at the same time.
Despite similar symptoms, allergies and colds have different causes.
Allergies occur when the immune system believes that a particular allergen is harmful to the body.
Upon exposure to this allergen, the immune system triggers certain cells to release a chemical called histamine.
Histamine is what causes itching, watery eyes, sneezing, runny nose, and other allergy symptoms.
For seasonal allergies, the trigger is often pollen from grass, trees, weeds, or other plants.
Seasonal allergies may develop during childhood or adolescence. Adults can also develop new seasonal allergens.
Some people may experience worse symptoms in different locations, since some areas have higher pollen counts for specific plants.
More than 200 different viruses can cause the common cold.
A type of virus family called rhinoviruses causes around half of all colds.
Other types of viral infections that can cause cold symptoms include:
- Coronaviruses (not the same one that causes COVID-19)
- Human parainfluenza virus
- Respiratory syncytial virus (RSV)
Because so many viruses can cause a cold, it’s not possible to test to identify the specific virus.
If your symptoms overlap with influenza or another illness, your doctor may run tests to rule these out.
How Contagious Are They?
Most viruses that cause colds are highly contagious.
They spread through droplets of saliva or mucus that are released during sneezing, coughing, and talking.
Cold viruses can also be spread from hand-to-hand contact and surface contact when the virus has contaminated shared objects such as doorknobs and countertops.
Most adults have an average of 2-3 colds per year. Children can have even more.
Both colds and allergies can seem to come on suddenly. But colds clear up faster than allergies do.
Seasonal allergy symptoms may come on nearly instantly when exposed to an allergen because your immune system begins releasing histamine as soon as you breathe in a trigger.
Seasonal allergies resolve when the trigger is no longer present in the environment.
In locations that experience four seasons, pollen activity can trigger allergy symptoms for up to seven months.
However, some months or seasons are worse for specific types of pollen, such as ragweed or tree pollen.
You should only experience symptoms during the months when your triggers are present.
Cold symptoms begin 1-3 days after exposure to a virus.
However, it can feel like a cold comes on suddenly since you may not know how or where you were exposed to a virus.
Colds typically resolve fully in 7-10 days.
If you have symptoms and aren’t sure if you have allergies or a cold, see a healthcare provider.
They will ask about your symptoms and how long they have lasted.
A medical provider can run tests to identify allergy causes.
The workup can include:
- Blood (immunoglobulin E) test: This tests for the presence of antibodies that build up in the blood in response to certain allergens. However, this test can cause false positives and may not be effective for some environmental allergens.
- Skin prick (scratch) test: This type of test can assess environmental, food, and some medication allergies. A healthcare provider tests for 10-50 allergens by placing small amounts of each allergen on the skin. Then they use thin needles to lightly prick or scratch the nearby skin. After about 15 minutes, they check for any reactions. (Typically a red rash or raised, round spots will develop in response to any allergies or sensitivities.)
Sometimes medical providers use both tests to assess or confirm a diagnosis.
Colds are typically diagnosed based on symptoms and by excluding other potential causes.
There is no specific diagnostic test for the common cold.
Seasonal allergies can range from mildly uncomfortable to disabling.
While there are no cures, home remedies and medications may help keep you comfortable.
You may be able to lessen allergy symptoms with the following strategies:
- Use a humidifier at home (do not use if you are sensitive to mold)
- Use HEPA air filters at home
- Stay inside when pollen counts are high
- Rinse sinuses with a neti pot or saline spray
You can find allergy medications over the counter or, for severe allergies, by prescription.
- OTC allergy medications: Daily OTC allergy medications include cetirizine (Zyrtec), levocetirizine (Xyzal), and loratadine (Claritin). Antihistamines that are taken on an as-needed basis, like diphenhydramine (Benadryl), may help with short-term allergy symptoms.
- Prescriptions: When OTC medications are not effective, a medical provider may prescribe other allergy medications. These could include antihistamines, corticosteroids, decongestants, mast cell stabilizers, or nasal sprays.
If you have a health condition or take any medications on a regular basis, talk to your doctor before starting any OTC medications for allergies.
Decongestants and antihistamines may interact with prescriptions or affect certain conditions like high blood pressure, kidney health, or liver health.
Treating a Cold
While there is no cure for a cold, some home remedies or medications may ease symptoms.
The following things can help to keep you comfortable while you’re recovering from a cold:
- Using a humidifier
- Diffusing certain essential oils, like eucalyptus or peppermint
- Gargling saltwater
- Staying hydrated
- Using vapor rub
Over-the-counter cold medications include pain relievers, decongestants, and antihistamines.
Read the instructions and talk to your doctor before starting OTC treatments.
Cold medicines may interact with prescriptions and may not be safe for some medical conditions, including pregnancy.
When to See a Medical Provider
While neither seasonal allergies nor a cold requires a trip to the doctor, a medical provider can recommend additional care and treatment options if you are unable to manage symptoms yourself.
Also seek medical care if:
- You have a cold that does not resolve
- You feel worse after 7-10 days
- You have a high fever (101ºF or higher)
How K Health Can Help
Did you know you can get affordable primary care with the K Health app? Download K to check your symptoms, explore conditions and treatments, and if needed text with a provider in minutes. K Health’s AI-powered app is HIPAA compliant and based on 20 years of clinical data.
Frequently Asked Questions
K Health has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.
Allergies and Hay Fever. (2021).
Common Colds: Protect Yourself and Others. (2021).
Understanding a Common Cold Virus. (2009).