According to the Centers for Disease Control and Prevention (CDC), adults can expect to have two to three colds a year. Children are likely to have even more colds every year.
Allergies are also 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.
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.
Although the symptoms of colds and allergies may be similar, there are also key differences.
Watery and itchy eyes are often a symptom of an allergy.
Variations in the history of the illness and duration of symptoms often offer clues as to which condition is present.
People should consider the following differences when trying to identify whether they have a cold or an allergy:
- Itchy and watery eyes are often telltale signs that the symptoms are due to an allergy
- A fever can occur with a severe cold, especially in children, but is not an allergy symptom
- A sore throat can occur with allergies but is more common with a cold
- Body aches also do not occur with allergies while they may be common with a cold
- Some people with allergies also develop eczema, which is not a symptom of a cold
Duration and history of symptoms
There is often a difference in how long symptoms of colds and allergies last. According to the CDC, cold symptoms typically last about 7 to 10 days. Allergy symptoms may last several weeks, particularly if the allergen remains in the air.
One of the main ways to tell the difference between a cold and an allergy is by the symptom history.
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.
Colds and allergies do share similar symptoms. For example, both conditions can affect the respiratory system. Common symptoms that can occur with either a cold or allergy include:
Nasal congestion may be a symptom of both colds and allergies.
- Runny nose
- Nasal congestion
- Sore throat
- Post-nasal drip
How to tell the difference
Asking certain questions can help 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.
Understanding the causes
In order to help identify the difference between a cold and an allergy, it's helpful to understand what each condition involves.
There are over 200 subtypes of viruses that can cause a cold with the rhinovirus being the most common. Colds are transmitted through droplets in the air from coughing and sneezing. Although colds occur more commonly in the winter, they can develop any time of the year.
An allergy is not caused by a virus and is not contagious. Instead, an allergy develops when the immune system reacts to a usually harmless substance as if it were dangerous.
The body releases compounds to combat what it perceives as a harmful substance. One compound released is histamine. This compound is intended to protect the body and fight the invader, but histamine causes many of the common allergy symptoms.
Although some over-the-counter medications target both colds and allergies, there are several differences in how each condition is treated.
If symptoms persist after 2 weeks, it may be recommended to visit a healthcare professional.
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.
However, there are some over-the-counter medications available to improve symptoms of a cold. These include decongestants to decrease nasal stuffiness and pain medication to help reduce a sore throat or body aches.
Prevention is often part of a plan to treat allergies. Once the allergen has been identified, individuals are advised to avoid it as much as possible. When avoiding an allergen is not possible, the symptoms can be treated in ways that differ from cold treatment.
Allergies can be treated with over-the-counter decongestants.
Medications containing antihistamines are used to treat allergies. Antihistamines block the effects of histamine, the compound that causes allergy symptoms.
Antihistamines, which usually come in a pill or nasal spray, may reduce common allergy symptoms, such as itchy, watery eyes, sneezing, and runny nose.
Nasal steroid sprays are also sometimes recommended to treat allergy symptoms. Nasal sprays containing corticosteroids decrease inflammation in the nose, which reduces congestion.
Allergy shots may also be used for long-term control of allergies. Allergy shots involve receiving small doses of the allergen at regular intervals over several months.
The goal of treating an allergy 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.
When to see a doctor
It is not always easy to tell the difference between a cold and an allergy, so it's important to know when to see a healthcare provider. If symptoms last for more than 2 weeks or if they are severe, it may be a good idea to see a doctor.
Doctors can identify allergy triggers through serum and skin tests. Once a specific allergen has been identified, an appropriate treatment plan is developed.