Why Does Coffee Cause Phlegm: The Surprising Connection

Coffee is a popular beverage enjoyed by many people around the world. It has a distinct aroma and flavor that can be quite addictive. However, some individuals may experience an unpleasant side effect when consuming coffee – an increase in phlegm production. This surprising connection between coffee and phlegm has puzzled many, and in this article, we will explore the reasons behind this phenomenon.

The Link between Coffee and Phlegm

Understanding Phlegm

Before delving into the connection between coffee and phlegm, it is essential to understand what phlegm is. Phlegm is a thick, mucus-like substance produced by the respiratory system. It serves as a defense mechanism to trap and eliminate foreign particles, such as bacteria and viruses, from the lungs and airways. Excessive phlegm production can indicate underlying respiratory issues, such as allergies or infections.

Acidity and Phlegm Production

One of the main theories behind the relationship between coffee and phlegm is the acidity of coffee. Coffee, especially when brewed strongly, contains high levels of acids. These acids can stimulate the production of mucus in the body, resulting in increased phlegm production.

When we consume acidic substances like coffee, the body reacts by producing more mucus to combat the acidity. This excess production of mucus can cause discomfort and lead to an increase in phlegm, which may contribute to coughing and congestion.

Stimulation of Gastric Acid

Another plausible explanation for the link between coffee and phlegm lies in its ability to stimulate gastric acid production. Coffee is a known stimulant, and it can trigger the release of gastric acid in the stomach. Increased levels of gastric acid can, in turn, lead to acid reflux, a condition where stomach acid flows back into the esophagus.

Acid reflux can irritate the throat and respiratory system, causing an increase in phlegm production. The irritation and inflammation caused by acid reflux activate the body’s defense mechanism, resulting in excessive mucus production. This excess mucus can then manifest as phlegm, contributing to the discomfort experienced by some coffee drinkers.

Factors Influencing the Effect

While the link between coffee and phlegm is apparent for some individuals, it is essential to consider that not everyone experiences this side effect. Several factors can influence the likelihood and intensity of phlegm production after coffee consumption.

Individual Sensitivity

Every individual reacts differently to various substances, and the same goes for coffee and its effects on phlegm production. Some people may have a higher sensitivity to the acids found in coffee, leading to increased mucus production. Others may have a more robust digestive system that can handle the acidity, resulting in fewer symptoms.

Pre-existing Conditions

Individuals with pre-existing respiratory conditions, such as asthma or chronic bronchitis, may be more prone to experiencing phlegm production after consuming coffee. These individuals already have compromised respiratory systems, making them more susceptible to stimuli that can aggravate their condition.

If you have a respiratory condition, it is advisable to consult with your healthcare provider about the potential effects of coffee on your symptoms.

Reducing Phlegm Production

If you enjoy coffee but find that it triggers phlegm production, there are steps you can take to minimize its effects.

Choosing a Milder Coffee

One option is to opt for a milder coffee with lower acidity. Light or medium roasts typically have a smoother and less acidic taste compared to dark roasts. Experimenting with different coffee beans and their roast levels may help you find a cup of joe that does not trigger excessive phlegm production.

Adding Milk or Cream

Another way to reduce the acidity of coffee is by adding milk or cream to your cup. Dairy products, especially milk, can help neutralize the acids present in coffee, making it gentler on your digestive system. This can potentially alleviate the phlegm production associated with coffee consumption.

Hydration and Water Intake

Staying adequately hydrated can also help in reducing the production of phlegm. Drinking plenty of water throughout the day can thin out the mucus and make it easier for the body to expel. Maintaining optimal hydration levels may alleviate the discomfort caused by excess phlegm production.


While the link between coffee and phlegm may be surprising to some, there are logical explanations behind this phenomenon. The acidity of coffee and its ability to stimulate gastric acid production can result in an increase in mucus production and, consequently, phlegm. However, it is important to note that not everyone experiences this side effect, and individual sensitivity and pre-existing conditions can influence the intensity of the symptoms.

If you find that coffee triggers excessive phlegm production for you, experimenting with milder coffee options or adding milk/cream to your cup may help alleviate the symptoms. Additionally, maintaining hydration levels is crucial in reducing the discomfort caused by excess phlegm.

As with any health-related concerns, it is always advisable to consult with a healthcare provider if you have persistent or severe symptoms. They can provide personalized advice and guidance to help manage your specific situation.

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