Cold and Flu Symptoms
Because cold and flu symptoms are similar, it's easy to mistake one for the other. In general, colds are milder than the flu. Fever, body aches, and dry cough are more common and intense with the flu. People with colds often have stuffy, runny noses, whereas people with the flu do not. Because signs and symptoms of cold and flu are so similar, a misdiagnosis could mean serious complications get overlooked.
The flu is like the cold in many ways -- basically, they're both respiratory infections caused by viruses. If a cold is misdiagnosed as flu, there's no problem. At worst, a cold can occasionally lead to secondary bacterial infections of the middle ear (otitis media) or sinuses (sinusitis), which can be treated with antibiotics. But if the flu is misdiagnosed as a bad cold, potentially life-threatening flu complications, such as pneumonia, may be overlooked.
Complicating the problem, many people get bad allergies in the fall, when ragweed pollen is at its peak in many areas, and winter can bring its own allergies as people spend more time indoors around pet dander and house dust mites (see Allergies vs Cold Symptoms).
Because some cold and flu symptoms are similar, it can be difficult (or even impossible) to tell the difference between them based on symptoms alone.
In general, flu symptoms are worse than the common cold, and symptoms such as fever, body aches, extreme tiredness, and dry cough are more common and intense. Colds are usually milder than the flu. People with cold symptoms are more likely to have a runny or stuffy nose. Colds generally do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations.