It hits you out of nowhere. You wake up with the symptoms of what seems like a cold: runny nose, cough, scratchy throat. Soon, you’re all stuffed up and headache-y. But is it truly a cold — or could it be a sinus infection?

“Symptoms from the common cold and a sinus infection, or sinusitis, often overlap — and it can be challenging to tell the two apart,” says Bu Jung Kim, MD, a family medicine provider at Geisinger. “But if you understand the key differences, you can effectively treat what’s ailing you and feel better soon.”

Most cases of the common cold and sinusitis are caused by viruses. In fact, more than 200 different viruses are known to cause colds. These viral infections should begin to improve in seven to 10 days.

In a few cases, however, sinus infections can be bacterial. These typically have more severe symptoms that can worsen after 10 days or more.

Cold vs. Sinus Infection Symptoms

Symptoms for the common cold can include:

• Runny nose
• Thick, typically clear mucus
• Sore throat
• Sneezing
• Coughing
• Headache
• Body aches, in some cases

If your cold symptoms don’t improve after 10 days, there’s a good chance it’s a more serious infection than the common cold, like a bacterial sinus infection.

While you can have sinus pressure with the common cold, facial pain and tenderness are telltale signs of a sinus infection. Sinusitis can also produce thicker mucus that is yellow or green, especially if it’s caused by bacteria.

Another good indication you have a sinus infection is if your “cold” starts to improve after a few days, then suddenly rebounds and worsens.

Symptoms for a sinus infection can include:

• Sinus pressure or pain behind the eyes and cheeks
• Fever and body aches
• Runny nose and post-nasal drip (mucus in the throat)
• Sore throat
• Headache
• Loss of taste and smell
• Bad breath

“For sinusitis, symptoms are more localized around your sinuses, such as around your nose and above your eyebrows, since the pathogen can cause inflammation in the sinus membranes, blocking mucus from draining,” says Dr. Kim.

Can a Sinus Infection Cause a Fever?

Yes, sinus infections can cause a fever — a typical response to any type of infection in the body. However, fevers aren’t a common symptom of sinus infections.

If you do get a fever from a sinus infection, it’s typically low grade, between 100.4° and 103° F.

“You can treat the fever at home with an over-the-counter medicine, such as acetaminophen or ibuprofen,” says Dr. Kim. “But be sure to seek medical attention if your fever lasts for three or four consecutive days or your symptoms don’t improve after 10 days.”

Are Sinus Infections Contagious?

It depends. Viruses from the common cold or flu that can cause sinus infections are contagious. You can pass on the cold or flu to another person, and that person may or may not develop a sinus infection.

A sinus infection caused by bacteria, allergies or a structural issue, such as a deviated septum, is not contagious. You don’t have to worry about passing illness to someone else.

Either way, if you don’t know the cause of your sinus infection, take precautions. Wash your hands often, cover your coughs and sneezes and keep your distance from others.

Cold vs. Sinus Infection: When to See a Doctor?

While most colds clear up on their own, it’s best to contact a doctor if:

• Cold symptoms don’t improve after 10 days
• Pain or discomfort becomes severe
• Fever lasts more than three days in a row
• Symptoms improve and then get worse

Your doctor can assess your symptoms and determine the best treatment. A bacterial sinus infection can be treated with antibiotics. But let your doctor decide whether you need them, due to their potential side effects if used inappropriately, Dr. Kim says.

A viral sinus infection and the common cold, however, are best treated at home by managing your symptoms, while your body builds up natural immunity and fights off the infection.

You can treat symptoms at home by getting plenty of rest and fluids, irrigating your sinuses with saline solution and taking hot, steamy showers. Acetaminophen or ibuprofen also can help.

“Distinguishing between a cold and sinus infection can be challenging,” says Dr. Kim, “but the sooner a diagnosis can be made, the sooner you can get the care you need and find relief.”