Colds are caused by hundreds of different viruses. When one of these viruses gets into your body, your immune system attacks it. Some of the effects of this immune response are the classic symptoms of a cold, such as congestion and coughing.
The germs that cause colds are contagious. You can pick them up when an infected person sneezes, coughs, or shakes hands with you. After a couple of weeks, at the most, your immune system fights off the virus and you should stop having symptoms.

Allergies are caused by an overactive immune system. For some reason, your body mistakes harmless substances -- such as dust or pollen -- for germs and attacks them. Your body releases chemicals such as histamine, just as it does when fighting a cold. This can cause swelling in your nasal passages, a runny nose, coughing, and sneezing. Allergies are not contagious, although some people may inherit a tendency to develop them.

Differences between Colds and Allergies

Characteristic	Cold	Allergy
Duration	three-14 days	Days to months -- as long as you are exposed to the allergen
Time of Year	Most often in the winter, but possible at any time	Any time of the year -- although the appearance of some allergens are seasonal
Onset of symptoms	Symptoms take a few days to appear after infection with the virus.	Symptoms can begin immediately after exposure to the allergen
Symptom	Cold	Allergy
Cough	Often	Sometimes
Aches	Sometimes	Never
Fatigue	Sometimes	Sometimes
Fever	Rarely	Never
Itchy, watery eyes	Rarely	Often
Sore throat	Often	Sometimes
Runny or stuffy nose	Often; usually yellow mucus	Often; usually clear mucus

Although there are some differences, cold and allergy symptoms overlap quite a bit. The most important difference is that colds usually don't last longer than 14 days. If you still have symptoms after two weeks, see your doctor. These may be allergy symptoms or a sign of another problem.

Prevention and Treatment of Colds and Allergies
Because the causes of cold and allergy symptoms are quite different, preventing them requires different strategies. To prevent allergy symptoms, avoid substances you're allergic to, called allergens. So if you're allergic to pollen, for instance, avoid going outside on days when the pollen count is high.

Here are some common allergens:

• Pollen
• Mold
• Animal dander
• Dust mites
• Cockroaches

To prevent cold symptoms, prevent the cold-causing virus from getting into your system.  Keep your distance from people who have colds. Wash your hands often. To protect others, always cover your mouth and nose (with a tissue or your sleeve, rather than your hands) when sneezing or coughing.

Do I have the flu? What are common flu symptoms?
Flu symptoms are usually more severe than cold symptoms and come on quickly. Symptoms of flu include sore throat, fever, headache, muscle aches and soreness, congestion, and cough. Swine flu in particular is also associated with vomiting and diarrhea.
Most flu symptoms gradually improve over two to five days, but it's not uncommon to feel run down for a week or more. A common complication of the flu is pneumonia, particularly in the young, elderly, or people with lung or heart problems. If you notice shortness of breath, let your doctor know. Another common sign of pneumonia is fever that comes back after having been gone for a day or two.
Just like cold viruses, flu viruses enter your body through the mucous membranes of the nose, eyes, or mouth. Every time you touch your hand to one of these areas, you could be infecting yourself with a virus, which makes it very important to keep hands germ-free with frequent washing to prevent both flu and cold symptoms.

So is it flu or cold symptoms?
How do you know if you have flu or cold symptoms? Take your temperature, say many experts. Flu symptoms often mimic cold symptoms with nasal congestion, cough, aches, and malaise. But a common cold rarely has symptoms of fever above 101 degrees. With flu symptoms, you will probably have a fever initially with the flu virus and you will feel miserable. Body and muscle aches are also more common with the flu.

This table can help determine if you have cold or flu symptoms.

Symptoms	Cold	Flu
Fever	Sometimes, usually mild	Usual; higher (100-102 F; occasionally higher, especially in young children); lasts 3 to 4 days
Headache	Occasionally	Common
General Aches, Pains	Slight	Usual; often severe
Fatigue, Weakness	Sometimes	Usual; can last 2 to 3 weeks
Extreme Exhaustion	Never	Usual; at the beginning of the illness
Stuffy Nose	Common	Sometimes
Sneezing	Usual	Sometimes
Sore Throat	Common	Sometimes
Chest Discomfort, Cough	Mild to moderate; hacking cough	Common; can become severe
Complications	Sinus congestion; middle ear infection	Sinusitis, bronchitis, ear infection, pneumonia; can be life-threatening
Prevention	Wash hands often; avoid close contact with anyone with a cold	Wash hands often; avoid close contact with anyone who has flu symptoms; get the annual flu vaccine
Treatment	Decongestants; pain reliever/fever reducer medicines	Decongestants, pain relievers, or fever reducers are available over the counter; over-the-counter cough and cold medicines should not be given to young children; prescription antiviral drugs for flu may be given in some cases; call your doctor for more information about treatment.

Usually, the time of year will give you some sense of what you're dealing with. The standard flu season runs from fall to spring of the next year.

When do I call the doctor with flu or cold symptoms?

If you already have flu or cold symptoms, it's important to call your doctor if you also have any of the following severe symptoms:

Persistent fever: This can be a sign of another bacterial infection that should be treated.

Painful swallowing: Although a sore throat from a cold or flu can cause mild discomfort, severe pain could mean strep throat, which requires treatment by a doctor.

Persistent coughing: When a cough doesn't go away after two or three weeks, it could be bronchitis, which may need an antibiotic. Postnasal drip or sinusitis can also result in a persistent cough. In addition, asthma is another cause of persistent coughing.

Persistent congestion and headaches: When colds and allergies cause congestion and blockage of sinus passages, they can lead to a sinus infection (sinusitis). If you have pain around the eyes and face with thick nasal discharge after a week, you may have a bacterial infection and possibly need an antibiotic. Most sinus infections, however, do not need an antibiotic.

In some cases, you may need to get emergency medical attention right away. In adults, signs of a crisis include:

• Severe chest pain
• Severe headache
• Shortness of breath
• Dizziness
• Confusion
• Persistent vomiting
• In children, additional signs of an emergency are:
  • Difficulty breathing or rapid breathing
  • Bluish skin color
  • Not drinking enough fluids
  • Lethargy and failure to interact normally
  • Extreme irritability or distress
  • Symptoms that were improving and then suddenly worsen
  • Fever with a rash

Can I prevent flu or cold symptoms?

The most important prevention measure for preventing colds and flu is frequent hand washing. Hand washing by rubbing the hands with warm soapy water for at least 20 seconds helps to slough germs off the skin.

In addition to hand washing to prevent flu or cold symptoms, you can also get a flu vaccine to prevent seasonal influenza. Seasonal flu activity in the United States generally peaks between late December and early March. Within two weeks of getting a flu vaccine, antibodies develop in the body and provide protection against flu. Children receiving the vaccine for the first time need two doses delivered one month apart.
Antiviral medicine may also help prevent flu if you have been exposed to someone with flu symptoms.

For more information, visit www.webmd.com/