Boogers don’t get much respect. But they’re part of one of your body’s built-in defense systems.

Here’s why boogers form, what different colors may mean and when to talk with a doctor.

Why Do Boogers Form

Your nose is constantly working to clean and protect the air you breathe. The lining of your nasal passages produces mucus that acts like a sticky filter, trapping dust, allergens and other particles before they reach your lungs.

Your nose also contains nose hairs and microscopic hairs called cilia. Together, they help filter debris and keep your airways clear. Cilia move in coordinated waves, pushing mucus toward your throat, where you swallow it without noticing.

As mucus dries inside the nose, especially near the front of the nasal passages, it forms a booger.

“You may notice more boogers when you’re exposed to allergens, smoke, dust or pollution; when you’re recovering from a cold; when you’re dehydrated; or when you spend time in dry air,” says Michael P. Angarone, DO, an infectious disease specialist at Northwestern Medicine. “In most cases, more boogers simply mean your nose is working harder to filter particles from the air you breathe.”

Why Are Boogers Worse in Winter?

If it feels like you have more boogers during the winter, you’re not imagining it.

Cold outdoor air and heated indoor air can dry out nasal passages, causing mucus to thicken and dry out more quickly. Winter also brings more colds and other respiratory infections, which can increase mucus production.

Using a humidifier, staying hydrated and treating underlying allergies can help keep your nasal passages more comfortable during colder months.

What Normal Boogers Look Like

Most normal boogers:

• Are clear, white or occasionally yellow
• Come and go with colds or allergies
• Improve within a week or two
• Aren’t accompanied by significant facial pain, fever or breathing problems

What Different Booger Colors Can Mean

Booger color can offer clues about what’s happening inside your nose, but color alone can’t diagnose an illness.

Clear or White

Clear mucus is normal and helps keep nasal tissues moist. White mucus may appear with mild congestion from allergies or a cold.

Yellow

Yellow mucus often develops when your immune system is responding to a virus, irritation or inflammation. It doesn’t automatically mean you need medical treatment.

Green

Green mucus is common during colds and upper respiratory infections. Despite popular belief, green mucus alone doesn’t mean you need antibiotics.

Red or Bloody

Blood-streaked mucus is usually caused by irritation from dry air, allergies, frequent nose blowing or picking your nose.

Brown or Black

Brown or black mucus can occur after exposure to dirt, dust, smoke or pollution and is often simply trapped debris being cleared from the nose.

Rarely, black mucus that doesn’t go away or has a foul odor may be a sign of a fungal infection, especially in the sinuses. This is more likely in people who have diabetes or weakened immune systems.

When To See a Doctor

Talk with your doctor if you have any of the following:

• Congestion lasting longer than 10 days or that worsens over time
• Fever
• Facial pain or pressure
• Frequent nosebleeds
• Persistent thick drainage
• Mucus with a foul odor
• Trouble breathing through your nose
• Symptoms affecting only one side of the nose

Is Picking Your Nose Bad?

Many people wonder whether picking your nose is harmful.

Occasional nose picking is common and usually not a major concern. Frequent picking, however, can irritate the nasal lining and cause bleeding, swelling or infection.

“Instead of picking, try to gently blow your nose into a tissue,” says Dr. Angarone. “You can also try saline spray or humidifiers to help soften and loosen dried mucus more gently. Handwashing before and after touching your nose can help reduce the spread of germs.”

Why Do Some Kids Eat Their Boogers?

Many children eat their boogers at some point. While the habit may be unpleasant, it’s common and usually not a cause for concern.

Children may do it out of curiosity, boredom or to clear their noses. Dry air, allergies and excess mucus can also make boogers more noticeable and increase nose-picking.

Parents can encourage children to use tissues, blow their noses and wash their hands regularly. Most children outgrow the habit as they get older.

How To Keep Your Nose Healthy

Simple daily habits can help keep your nasal passages healthy and your mucus normal:

• Stay hydrated
• Use a humidifier when indoor air is dry
• Manage allergies
• Avoid tobacco smoke and other irritants
• Use saline spray when needed

These steps can help keep mucus moving and support your nose’s ability to filter the air you breathe.

Your Body’s Natural Defense

Boogers may be a funny topic, but they play an important role in protecting your respiratory system.

Every day, your nose traps dust, allergens, germs and other particles before they can make their way deeper into your airways. Working together, mucus, nose hairs and cilia help filter and clear those unwanted visitors.

“Most boogers are completely normal,” says Dr. Angarone. “Changes in color or texture often happen because of allergies, irritation or a common cold. But persistent congestion, frequent nosebleeds or worsening symptoms deserve medical attention.”

Boogers rarely get much respect, but they’re one small sign that your body’s built-in defense system is working exactly as it should.