If you’ve got the common cold, don’t take it lightly. Here are 7 symptoms why your seemingly harmless illness may be something more threatening.

It seems like every day you head into the office in the winter, you risk coming home with a cold. But is every sickness you come down with actually a cold—or might it be something else?

That’s actually an important distinction to make, since how you’d treat a cold could be pretty different than how you’d treat another kind of illness.

In most cases, colds are nothing major: “The vast majority of these upper respiratory infections are caused by a virus, which means you don’t need to go to a doctor or take antibiotics,” says Mina Le, M.D., otolaryngologist at the West Palm Beach VA Medical Center. “You’re best off resting, hydrating, and irrigating your sinuses with saline.

But if you have something else, that could be more serious—and, at the very least, it would require a visit to your doctor.

That’s why it’s important to know the symptoms that your simple cold might be something more sinister. Here are the 7 symptoms you need to know.

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YOU’VE GOT A FEVER AND NOTHING ELSE

“A common cold will rarely cause a fever,” says Michael Benninger, M.D., otolaryngologist at the Cleveland Clinic.

A fever—a temperature above the average body temperature of 37 degrees Celcius—usually suggests something more aggressive, like the flu instead of a cold, or a bacterial infection, like a skin infection or pneumonia.

It can be difficult to determine if the infection is caused by a viral or bacterial infection.

“If it is very high (above 38 degrees Celcius) and seems different than other illnesses you have had before, you should probably be evaluated,” says Paul C. Bryson, M.D., otolaryngologist at the Cleveland Clinic.

That’s because there’s a serious cause of fever you need to know about: meningitis. In this case, you may also have other signs like severe headache, confusion, neck pain or rigidity, or change in vision, says Dr. Benninger.

YOU’VE GOT A PHLEGMY COUGH WITH THE FEVER

This one could be serious, too: pneumonia.

“If you have a cough and then develop a fever, it could be suggestive of a pneumonia, which requires early treatment,” says Dr. Benninger. “So getting to the doctor with a cough, particularly if productive (mucus-filled) is important.”

If you have pneumonia, you may also notice symptoms like a fever higher than 38 degrees Celcius, chest pain, and severe fatigue that may also cause confusion or changes in your mental capabilities.

But not every kind of pneumonia completely knocks you on your butt. You may also have walking pneumonia, a less serious form of pneumonia. It’s usually caused by a lung infection from a bacteria called Mycoplasmapneumoniae. While it may mimic a cold, the biggest indicators are chest pain and a violent cough.

YOU’VE GOT A BAD SORE THROAT

Well, colds do come with sore throats, but if your sore throat is really severe, that can point to something else—especially if you’re not sneezing, sniffling, or feeling congested.

“A very bad sore throat can be tonsillitis,” says Dr. Benninger. “If the tonsils are swollen and red and there are white patches on them, it is likely tonsillitis (viral pharyngitis) or strep throat.”

You may have a fever too, so see your doctor. He or she will perform a culture, and if it comes back positive for strep bacteria, you may need to take antibiotics.

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YOU’RE STUFFED UP AND YOUR FACE HURTS

It could be a bacterial sinus infection, which could require antibiotics.

“An early fever higher than 38 degrees Celsius can signal a bacterial sinus infection, which is diagnosed when you have facial pain, a blocked-up nose, and creamy white, nasal drainage that either worsen or don’t improve within ten days,” says Dr. Le.

Congestion and nasal discharge is also common with colds, too, but there are four key differences that may signal a sinus infection instead, according to the Cleveland Clinic. These include that 10-day-or-more duration, sinus pressure or pain, yellow or green mucus instead of clear, and bad breath.

YOU’VE GOT STOMACH ISSUES, LIKE VOMITING AND DIARRHEA

Average cold symptoms are felt from the lungs up—fever, headaches, cough—not in the stomach and below. So if you’re on the toilet, it’s likely something else.

“The most common is viral gastroenteritis, or what is called the stomach flu,” says Dr. Benninger. “This can be pretty intense with watery diarrhea and vomiting but tends to be self limited. It tends to come on fairly quickly but usually resolves over one to two days.”

Another cause? Food poisoning, which can cause similar symptoms, but occurs after eating contaminated food.

YOU HAVE BODY ACHES OR CHILLS

Body aches or chills likely come into play with fever, which, as we said above, usually doesn’t occur with a simple cold.

“These are common with both viral and bacterial illnesses and are usually in context of a febrile illness (fever-induced illness),” says Dr. Bryson.

So if you have a fever, along with body aches or chills, it likely indicates you have something like the flu instead of a simple cold.

YOU HAVE COUGHING, SNEEZING, AND A SORE THROAT— AND IT GETS WORSE FROM THERE

Yeah, those symptoms are common with a cold. But the thing that separates these symptoms that occur with a cold from those that come with the flu is the fact that other, more uncomfortable symptoms usually follow.

With a flu, the coughing, sneezing, and sore throat tends to be more severe, and is followed by headache, muscle aches, and fatigue, says Andrew Pekosz, Ph.D., professor of molecular microbiology and immunology at Johns Hopkins University Bloomberg School of Public Health.

“It is very hard to determine if you have the flu solely by the symptoms you experience,” says Pekosz. “The only way to be sure if you have influenza is to get a special test that can administered by your health care provider.”

SO WHAT CAN YOU DO ABOUT YOUR SYMPTOMS?

“There are drugs that can help reduce influenza disease severity, but they must be given within 48 hours of symptom onset for them to be effective,” says Pekosz. “In general, if your symptoms progress to a stage where you are having trouble breathing or your coughing generates pain in your chest, you should seek medical help immediately.”

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