According to a report by CNN, patients with COPD may need to moderate their alcohol consumption due to the chemical effects of drinking on airway clearance.

One important effect: alcohol can alter certain functions of your airways, notably mucociliary clearance. A layer of mucus covers the tissue that lines your airways within your respiratory system. Tiny hairs called cilia beat rapidly back and forth and propel the mucus forward through your air passages to keep them clean. This process filters out dust and other particles that you might have inhaled. When the process doesn’t work correctly, you’re more likely to get sick from infections caused by bacteria and viruses that don’t get cleared out. That’s dangerous because your ability to breathe well is already compromised by the COPD.

If you’re an occasional drinker, you probably don’t need to worry. Research suggests that modest amounts of alcohol may not have a negative impact on this process. However, chronic alcohol use may impair your airway’s ability to clear out all those pathogens. In fact, some experts warn that heavy alcohol use may even contribute to a higher incidence of lung infections—the very lung infections that a person with COPD needs to avoid.