Do You Have An Allergy Or A Cold? How To Tell The Difference

Allergy and cold symptoms can be very similar. Problems from both include nasal congestion, sneezing, cough, headache, fatigue and malaise (just feeling bad).

How can one discriminate between a cold and allergies? It’s not always easy but there are some subtle differences, which we will point out for you in this article.

Woman with allergy or cold symptoms


Even though they may feel the same, the underlying cause for allergies and a cold are different. The latter is brought on through an infection by a virus. There are many respiratory viruses that cause cold symptoms. A virus is a germ that cannot survive on its own in nature. It needs to infect a host (you) and use genetic material from the host’s cells in order to reproduce.

Allergies are caused by exposure to protein substances called allergens in the environment that stimulate the body to react. The individual with an allergy is usually born with the genetically programmed sensitivity to a particular allergen. Allergens can be inhaled like pollen or ragweed or ingested like peanuts or seafood allergies. There are contact allergic reactions as well, such as that to poison ivy.


Different cause – Same reaction

The reason that a cold and allergies can produce similar symptoms is that the body reacts to both the virus and the allergen as a foreign substance.

A viral particle is still made up of protein and is no different to the body’s immune system than an environmental allergen. The same initial immune response is generated to both invading particles. The body doesn’t care if it’s allergic or viral, it sends out the first line of defense to contain it.

In the case of viral infection, the body will generate a second immune response that involves identification of the organism and production of organism specific antibodies.


Clues to Diagnosis

There are some clues that can help discriminate between a viral cold and an allergy.Woman with allergy remedy treatments

  • Fever- The generalized inflammatory reaction of the body to allergies may make the sufferer feel warm, but running an elevated temperature is unusual. Any fever above 30 degrees Celsius (101 degrees Fahrenheit) is more indicative of a cold.
  • Length of illness- Viral infections last generally seven to ten days. Any symptoms that persist past 10 days are more suspicious for allergies.
  • Cyclic history- While it is possible to contract a viral cold at the same time every year, it would be an unusual coincidence. Annual (seasonal) symptoms tend to suggest allergic reactions to something blooming in the environment.
  • Onset of symptoms- It may be difficult to determine but allergic symptoms develop directly after exposure to the allergen. Cold symptoms take a few days after infection to produce a response.
  • System progression- A virus will produce symptoms in the organs it infects. A progression of symptoms can be noticed from initial sore throat to head congestion, then involving chest congestion and perhaps developing nausea and vomiting if the virus infects the upper gastrointestinal tract. Each cold virus presents a different pattern but symptoms will change over time as the virus reproduces and moves through the body. Because the body has already been sensitized to allergens, the allergic reaction typically stimulates symptoms in target locations simultaneously. There is little or no progression of symptoms.
  • The community- The infective nature of a virus would make it unlikely that only one would be affected in the immediate environment. Of course there is always one that starts it, but in general if others around are getting sick with similar symptoms it is more than likely a cold.


Why It Matters

Even though both conditions are usually self-limiting and non-life threatening, there are reasons to identify whether the symptoms come from a cold or and allergy. If it is a viral infection, steps may be taken to prevent spreading the infection to family, friends and co-workers. Taking a day or two off from work may help limit exposure. It won’t matter if allergy is the cause, as this cannot be spread! Using a hand sanitizer is a good general practice that becomes paramount if sick with a cold.

The treatments for both viral colds and allergies are usually intended to control symptoms are can therefore be similar. They may include decongestants and anti-histamines orally and topically as a nasal spray, acetaminophen (paracetamol) or non-steroidal anti-inflammatories like ibuprofen for fever and pain or steroids if symptoms are severe. Antibiotics are not recommended for either condition.

If symptoms become severe or persist, seek a medical evaluation, it may not be a simple allergy or common cold.

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