Because the symptoms of colds and allergies are often similar, it can sometimes be difficult to tell the difference between the two. Despite the sometimes overlapping symptoms between these two conditions, the causes of these diseases are very different. For example, colds are caused by more than 200 different viruses that can be picked up from various places (other people, money, doorknobs, food, etc). Once the cold virus enters the body, the immune system kicks its defenses into overdrive causing the body to release different chemicals, resulting in the typical symptoms associated with the common cold.
Allergies, on the other hand, are not caused by viruses. Rather, they result from an overactive immune system that identifies harmless substances such as pollen, pet dander, pet hair, or dust as potential threats in some individuals. In this case, the body releases different chemicals to fight the allergy than it would a cold. Despite the different mechanism, the symptoms associated with allergies are often similar to that of the common cold, namely nasal congestion, sneezing, and runny nose.
Although both allergies and colds can result in congestion, sneezing, and runny nose it is important to know that there are symptoms that are distinct between the two disorders. Allergies often lead to itchy, watery eyes, something that does not often happen with a cold, while colds are often accompanied by coughing and a sore throat, symptoms not usually associated with allergies.
The differences in duration and symptoms between cold and allergies are shown in the table immediately below.