Cold, Flu, Swine Flu, or Allergies?

Let’s go through the symptoms of each of these illnesses separately first, then compare them:

Swine flu, or the H1N1 strain of influenza, is a new virus that appears to have arisen through some intermixing of the influenza viruses normally found in humans, pigs, and birds. It causes symptoms similar to the standard seasonal flu, including the sudden appearance of fever (anything above 100 F, in this case), cough, and sore throat. Some people also get a runny or stuffy nose, fatigue, body aches, headache, and joint and muscle aches. People can get diarrhea and vomiting with swine flu, which are symptoms that are unusual with regular seasonal flu.

The symptoms of swine flu can be different in young children and frail older adults, and flu of any sort can be hard to recognize when it affects the very young or old. Small children may just seem sick and out of sorts, with fast breathing or pulse, or might act very sleepy or irritable. Older folks might complain of severe body aches, or become dehydrated or confused. Most people who get swine flu do not become very sick with it. Symptoms begin to improve within two to five days, although it may take several weeks to feel completely normal again.

Seasonal flu causes sudden onset of fever, body ache, headache, and fatigue, with cough or sore throat. Body aches may be very prominent, particularly in older adults who may complain only of severe back pain. Vomiting and diarrhea are not usually part of seasonal flu. Regular flu is less contagious than swine flu, but it makes most people feel pretty sick.

Colds are mostly caused by rhinoviruses. These viruses usually settle in a limited part of the body (nose and throat, eye, ear, or chest). They can cause fever and sometimes fatigue and body aches, but generally do not make people as sick as influenza viruses.

Allergies can cause stuffy nose, sneezing, runny nose, and itching of the nose, eyes, throat, and skin. Allergies can make the eyes swell and look bloodshot. Occasionally, people will feel chilled, but measurable fevers are uncommon and the symptoms usually do not have the same time course as those of a cold or flu. Asthma can cause cough, but other chest symptoms, like shortness of breath, wheezing, and chest tightness are just as common.

Depending on what the person is allergic to, the symptoms may last a few weeks or become chronic during certain times of the year. The person may have good days and bad days and the overall pattern is waxing and waning. Compared to colds and flu, allergies cause more prominent itching, minimal fever and body ache, and tend to build up and subside over longer periods of time.

Clearly, there are many symptoms that flu, colds, and allergies share, but there are other bits of information that help clinicians determine which problem is likely to be present. For example, if other people around you have recently been sick with similar symptoms, then colds or flu are much more likely. If you have similar symptoms at the same time every year, then allergies are higher on the list. Health care providers also use information from the government, the news, and other sources, as well as the knowledge they get from seeing patients all day long, to determine whether colds or flu are circulating in the community.