What Are the Causes of Phlegm When Swimming?

Swimming is a good way to exercise and help you lose weight, strengthen your muscles and improve your overall health. However, you may experience an increase in phlegm inside your sinuses shortly after or during a swimming session. There are many different causes associated with the buildup of phlegm in your nasal passages, some of which are brought on by swimming or being submerged in water. Phlegm buildup can also be brought on by other medical conditions.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.


While you are swimming, it is possible to have water naturally enter your nasal passages in a minor amount despite holding your breath when submerged. As such, your body naturally responds by producing phlegm inside your sinuses. This buildup of phlegm can cause you to hack or cough, even to the point of needing to spit. While this buildup is a natural bodily response, there are a few examples of other medical conditions that can cause phlegm production while swimming.

Asthmatic Bronchitis

One example of such a medical condition is asthmatic bronchitis. Asthmatic bronchitis is associated with symptoms such as wheezing, coughing, shortness of breath, coughing up mucus or phlegm and an overall issue with breathing normally. Bronchitis is marked by an inflammation of the bronchial tube lining. This condition can be made worse by physical activity such as exercising or swimming and can cause you to become fatigued quickly due to lack of oxygen in your lungs. Treatment can include a prescribed inhaler.

Swimming Induced Pulmenary Edema

Another possible condition that can cause a buildup of phlegm in your nasal passageways is swimming-induced pulmonary edema, or SIPE 2. According to Charles C. Miller, Jr., Ph.D., this condition can also cause a "flooding" of your lungs as they begin to fill with blood, phlegm or other liquids when submerged in deep water. Swimming can increase the severity of this condition due to a combination of factors "that creates what can be thought of as a 'perfect storm' that leads to capillary leak." When left untreated, this condition can cause additional medical disorders such as cardiac arrest or lung failure.


If you begin to experience a shortness of breath during or immediately following swimming, be sure to take a rest for a few minutes to regain your composure. Coughing up a minor amount of phlegm is relatively normal due to your body's natural response to swimming. However, if you experience breathing difficulties for more than 30 minutes, seek medical attention as a means to rule out any additional severe complications.