Yellow phlegm can be a sign of an infection or illness that may cause asthma symptoms to worsen. A person with asthma should take note of the color of their phlegm, as certain colors may mean they should contact a doctor.

Phlegm, or sputum, is a thick mucus that is different from saliva. People cough up phlegm from their lungs.

The body can produce excess phlegm when a person has certain health conditions. Different conditions can cause the phlegm to take on various colors.

This article will explain the possible causes of yellow phlegm in people with asthma. It will give treatment options for these causes and advise when a person should contact a doctor.

there is a black and white photo of a person coughing into a tissueShare on Pinterest
Cavan Images/Getty Images

Some people with asthma produce excess phlegm, but yellow phlegm could be a sign of infection.

Producing phlegm of any color can be a sign that a person’s airways are becoming inflamed. Airway inflammation may also cause other asthma symptoms, such as:

If a person’s airways become too inflamed, they may narrow, causing an asthma attack. In that case, a person can use a rescue inhaler to expand their airways and make breathing easier.

Yellow phlegm is not normal and can be a sign that an infection is present.

Yellow or green phlegm may be a sign that a person has developed an infection such as:

Infections often worsen asthma symptoms, which can be dangerous. This is why it is important for a person with asthma to keep using their preventer inhaler to manage their symptoms.

Yellow phlegm can also be a sign that a person has developed any of several possible illnesses. Yellow phlegm may turn into green phlegm over time if the illness worsens and more white blood cells and debris are present in the mucus.

Below are some common illnesses that cause a person to produce yellow and green phlegm.

Bronchitis involves swelling and inflammation in the bronchial tubes, which link the mouth and nose with the lungs. Initially, a person may have a sore throat and a dry cough, which can cause clear or white phlegm to develop.

Over time, the phlegm may turn yellow or green, which may be a sign that a secondary bacterial infection has developed.

In addition to the production of yellow or green phlegm, bronchitis can cause a variety of other symptoms. Symptoms of acute bronchitis last longer than 3 weeks and include:

Pneumonia is an infection of the lungs that has a variety of possible causes. Pneumonia causes the lungs to become inflamed and the alveoli inside the lungs to fill up with fluid.

A person with pneumonia may cough up yellow or green phlegm.

Other symptoms of pneumonia include:

Pneumonia can be viral, bacterial, or fungal. Doctors will treat pneumonia in various ways depending on the type.

Sinusitis is inflammation of the sinuses, or nasal passages. Sinusitis can result from viruses, bacteria, fungi, allergies, or autoimmune reactions.

A common symptom of sinusitis is yellow or green phlegm and nasal discharge.

Other common symptoms include:

The color of phlegm can tell a lot about the condition of a person’s respiratory system. Below is an outline of some of the colors and what they mean.

If a person with asthma notices phlegm that is red, brown, or black, they should speak with a doctor right away, even if they notice only a small amount of these colors.

Clear phlegm

Healthy phlegm is usually clear. However, if a person produces large amounts of clear or white phlegm, it may be a sign that their airways are inflamed.

Large amounts of clear or white phlegm may also mean that a person’s asthma symptoms are getting worse.

A person may wish to use their preventer inhaler to deal with worsening asthma symptoms.

Brown phlegm

Brown phlegm often appears in people who smoke. It could mean that there is dried blood in the mucus.

Brown or rust-colored phlegm can also mean that a person may have bacterial pneumonia or bacterial bronchitis.

Brown phlegm warrants contacting a doctor as soon as possible.

White phlegm

White phlegm may be a sign that a person has nasal congestion. This can cause the mucus to pass through the respiratory tract more slowly and to become thicker and turn white.

White phlegm may also be a sign that a person has any of the following conditions:

Red or pink phlegm

The main cause of red or pink phlegm is the presence of blood. A person may have blood in their phlegm if they have been coughing a lot due to a respiratory infection.

However, several other conditions can also cause blood to be present in a person’s phlegm, including:

A person with red or pink phlegm should contact a doctor as soon as possible.

Black phlegm

Black phlegm can be present if someone has inhaled large amounts of a black substance, such as coal dust.

Smoking cigarettes may also cause black phlegm.

Phlegm or mucus may also look black or dark because of bleeding in the airways. Conditions that can cause bleeding in the airways, and therefore cause dark-colored mucus, include:

A person who notices black phlegm should contact a doctor right away.

If a person with asthma has phlegm that turns yellow or green, they may want to wait a few days to see whether it returns to normal. But if the phlegm remains yellow or green for more than a few days, a person should make an appointment with a doctor.

They should also monitor their other asthma symptoms just in case they begin to get worse.

If a person with asthma notices phlegm that is red, brown, or black, they should contact a doctor right away, even if they notice only a small amount of these colors. These colors could indicate a more serious condition.

Phlegm, or sputum, is a thick mucus that the body produces. People cough up phlegm from their lungs and respiratory tract.

A person with asthma may produce excess phlegm. If a person with asthma produces yellow phlegm, it may be a sign of an infection or another condition. Common conditions that cause phlegm to turn yellow include pneumonia, bronchitis, and sinusitis.

A person should contact a doctor if they have been producing yellow phlegm for longer than a few days.