You can reduce phlegm by staying well hydrated, humidifying your air, and using simple techniques like steam inhalation and saline rinses to thin and move mucus out of your airways. Most phlegm buildup resolves within a week or two when caused by a cold or allergies, but persistent congestion benefits from a more deliberate approach combining several of these strategies.
Phlegm is mucus produced in your lower airways and lungs. Your body makes it constantly as a protective layer, trapping dust, bacteria, and other irritants. The problem starts when infections, allergies, or environmental triggers cause your airway glands to ramp up production. An infection thickens mucus with bacteria and immune cells, which stimulates even more mucus production in a frustrating cycle. Allergies trigger a similar cascade: your immune system releases histamine, which swells the membranes lining your nose and airways and kicks the mucus glands into overdrive.
Drink More Fluids to Thin Mucus
The thickness of your phlegm is directly tied to how hydrated your airways are. Research on airway surface liquid shows a strong correlation between mucus solid content and its effective viscosity. In other words, the drier your mucus, the thicker and stickier it becomes, and the harder it is for the tiny hair-like structures in your airways (cilia) to push it along.
When the fluid layer lining your airways is well maintained, mucus transport nearly doubles in speed. In lab models, restoring fluid to dehydrated airways increased mucus clearance from about 7 millimeters per minute to nearly 13. You don’t need a special drink to achieve this. Water, broth, herbal tea, and warm liquids all help. Warm fluids have the added benefit of loosening congestion as you drink them. Caffeine and alcohol can be mildly dehydrating, so they’re not your best options when you’re already congested.
Use Steam to Loosen Congestion
Breathing in warm, moist air helps soften thick phlegm so it’s easier to cough up or blow out. The standard approach is simple: place a towel over your head, lean over a bowl of recently boiled water, and inhale the steam for about five minutes. You can do this once or twice a day while symptoms last.
A hot shower works too, especially first thing in the morning when overnight congestion tends to be worst. The key is moist heat reaching your airways, not the specific method. Be careful with the water temperature. Burns from steam inhalation are a real risk, particularly for children. Keep your face far enough from the bowl that the steam feels warm but not painful, and never let young children lean over hot water unsupervised.
Keep Indoor Humidity Between 40% and 60%
Dry indoor air pulls moisture from your airway lining, thickening mucus and slowing its clearance. This is especially common in winter when heating systems run constantly. Maintaining indoor relative humidity between roughly 40% and 60% is the sweet spot for respiratory comfort and overall health.
A cool-mist humidifier in your bedroom can make a noticeable difference overnight. If you go above 60% humidity, though, you create conditions that encourage mold and dust mites, both of which trigger more mucus production in people with allergies. A simple hygrometer (available for a few dollars at hardware stores) lets you monitor your levels. Clean the humidifier regularly to prevent it from becoming a source of irritation itself.
Try a Saline Rinse
Flushing your nasal passages with salt water physically washes out excess mucus, allergens, and irritants. It’s one of the most effective non-drug approaches for both acute congestion and chronic sinus issues. You can use a neti pot, squeeze bottle, or bulb syringe.
The recommended salt concentration for a homemade rinse is 2% to 3.5%, which works out to roughly one-quarter to one-half teaspoon of non-iodized salt per cup of water. Always use distilled, sterile, or previously boiled water. Tap water can contain organisms that are harmless in your stomach but dangerous in your sinuses. Clean your rinse device thoroughly between uses. Most people tolerate once or twice daily rinsing well during active congestion.
Adjust Your Sleeping Position
Lying flat lets mucus pool in your throat and chest, which is why congestion often feels worse at night and first thing in the morning. Elevating your head and upper body by 30 to 45 degrees, using an extra pillow or a wedge, helps gravity pull mucus downward toward your larger airways where it’s easier to clear.
For more stubborn chest congestion, postural drainage positions can help. This involves lying in specific orientations (on your side, on your stomach, or with your head slightly lower than your chest) for several minutes to drain mucus from different sections of your lungs. Lying on your side with the congested lung facing up, for example, lets gravity pull mucus toward the center of your chest where a cough can move it out. Gently tapping or vibrating your chest wall during these positions can further loosen phlegm.
Consider an Expectorant
Guaifenesin is the only over-the-counter expectorant available in the United States. It works by thinning mucus in your airways, making it easier to cough up. The standard adult dose is 200 to 400 milligrams (typically 2 to 4 teaspoonfuls of liquid) every four hours, with no more than six doses in 24 hours. It’s available in both liquid and tablet form, often combined with other cold medications, so check labels carefully to avoid doubling up on ingredients.
Guaifenesin works best when paired with plenty of fluids. Without adequate hydration, the medication has less raw material to work with. It won’t stop your body from producing phlegm, but it makes what’s there easier to move. If you’re dealing with a productive cough, avoid cough suppressants during the day. That cough is your body’s mechanism for clearing the mucus, and suppressing it can leave phlegm sitting in your airways longer.
Foods That Help (and One That Doesn’t)
Spicy foods containing capsaicin, the compound that gives chili peppers their heat, stimulate sensory nerves in your airways. This triggers a brief surge of watery mucus secretion that can help flush out thicker, stickier phlegm. If you’ve ever had a runny nose after eating hot salsa, that’s the mechanism at work. It’s a short-term effect, but it can provide temporary relief when you’re feeling stuffed up.
Warm broths and soups combine hydration, warmth, and steam in one package, making them genuinely useful for congestion. Honey, particularly in warm water or tea, can soothe an irritated throat and may help calm the cough reflex, though its direct effect on phlegm itself is modest. Dairy, on the other hand, gets an undeserved reputation. Despite the widespread belief that milk increases mucus, controlled studies have not confirmed this. Dairy may coat the throat temporarily and create the sensation of thicker mucus, but it doesn’t actually increase production.
Avoid Common Triggers
Cigarette smoke is one of the most potent drivers of excess phlegm. It dehydrates your airway lining and increases mucus viscosity, nearly doubling the effective thickness of mucus compared to non-smokers. It also impairs the cilia that sweep mucus upward, so you produce more of it and clear less. People with smoke-related lung disease have mucus with significantly higher solid content (roughly 2.8%) compared to non-smokers (about 1.6%), making it far harder to move.
Beyond smoking, common environmental triggers include dust, pet dander, mold, strong fragrances, and cleaning chemicals. If allergies are driving your phlegm, reducing exposure to your specific triggers will do more than any remedy. Cold outdoor air can also cause a temporary increase in watery mucus production, so breathing through a scarf in winter helps.
What Phlegm Color Actually Tells You
Many people try to diagnose themselves based on phlegm color, but the picture is less clear-cut than commonly believed. Green or yellow phlegm does correlate with higher bacterial loads when assessed on a standardized color chart, but patient self-reporting of color turns out to be unreliable as a marker of bacterial infection. Even white or gray (mucoid) sputum showed bacterial growth in 78% of samples in one study.
That said, some patterns are worth noting. A deepening color progression from yellow toward brown is associated with certain gram-negative bacteria. Blood-tinged phlegm can result from something as minor as forceful coughing that irritates your airway lining, but it can also signal something more serious. Phlegm that persists beyond three weeks, changes dramatically in color or volume, or comes with fever, shortness of breath, or chest pain warrants a professional evaluation. Color alone isn’t enough to determine whether you need antibiotics.