Asthma attacks happen when something triggers three simultaneous responses in your airways: the muscles around them tighten, the lining swells with inflammation, and the passages fill with excess mucus. Together, these responses drastically narrow the space air has to move through, causing wheezing, chest tightness, coughing, and shortness of breath. Roughly 363 million people worldwide had asthma in 2023, and the condition caused 442,000 deaths that year.
What Happens Inside Your Airways
Your airways are lined with smooth muscle that normally relaxes and contracts gently to regulate airflow. During an asthma attack, that muscle contracts far more forcefully than it should for an airway of its size, and the contraction spreads unevenly across different parts of your lungs. This alone would make breathing harder, but it’s only the first layer of the problem.
At the same time, your immune system floods the airway walls with inflammatory cells, causing the tissue to swell inward. The cells lining your airways begin producing thick, sticky mucus in quantities they normally wouldn’t. Between the muscle squeezing from the outside, the swelling pushing inward, and the mucus clogging what’s left of the passage, airflow drops sharply. This is why an attack can feel like trying to breathe through a narrow straw.
Allergic Triggers
For many people with asthma, attacks start with an allergic reaction. The most common culprits are pollen, dust mites, pet dander, mold spores, and cockroach particles. When your immune system first encounters one of these substances, it mistakenly flags it as dangerous and produces antibodies called IgE that are specifically tuned to that allergen. Those antibodies stay in your body, waiting.
The next time you inhale that allergen, IgE antibodies recognize it immediately and signal your immune system to release histamine and other chemicals into the bloodstream. In some people, this cascade stays in the nose and eyes (hay fever). In people with asthma, the same reaction hits the lungs and airways, triggering the muscle tightening and inflammation that produce an attack. This is why allergies and asthma so often go together: the same substances that give you a runny nose can also close down your airways.
Non-Allergic Triggers
Not every asthma attack involves an allergen. Many triggers provoke airway narrowing through direct irritation or physical changes in the airways themselves.
Cold, dry air. For years, cold air was blamed for exercise-related attacks. More recent research points to dryness as the real problem. Cold air holds less moisture than warm air, so breathing it in rapidly dehydrates the lining of your airways. That dehydration causes the passages to narrow and restrict airflow. This is why winter air and air-conditioned environments can both be problematic.
Exercise. Physical exertion forces you to breathe harder and faster, usually through your mouth rather than your nose. Your nose normally warms and humidifies incoming air. Bypassing it means your airways get hit with a larger volume of dry air in a short time, which can trigger the same dehydration response.
Respiratory infections. Colds, flu, and other viral infections inflame airways that are already prone to overreacting. For many people with asthma, a simple upper respiratory infection is the single most common trigger for a serious flare-up.
Strong emotions and stress. Laughing hard, crying, or acute stress can change your breathing pattern and stimulate the nervous system in ways that tighten airway muscles.
Workplace and Chemical Irritants
Over 300 known substances in workplace settings can cause or worsen asthma. These include chlorine-based cleaning products, wood and grain dust, flour, metal dust, ammonia, isocyanates (common in spray paints and foams), and solvent vapors. Even green coffee bean dust is a recognized trigger. Cigarette smoke, strong fumes, and ozone exposure round out the list.
Some of these substances cause asthma through the same IgE-driven allergic pathway as pollen or dust mites. Others irritate the airways directly, provoking inflammation and muscle spasm without involving the immune system’s allergic machinery at all. People who develop asthma symptoms for the first time as adults often trace the onset to workplace exposure, which is why occupational asthma is considered a distinct category.
Why Attacks Are Worse at Night
If your asthma tends to flare up in the early morning hours, your body’s internal clock is a major reason. Research from Harvard Medical School found that lung function in people with asthma hits its lowest point during the circadian night, around 4 a.m. This happens because your body’s central clock, along with smaller “clocks” throughout your tissues, naturally cycles hormone levels, immune activity, and airway tone on a 24-hour rhythm. During the nighttime phase of that cycle, airway resistance increases on its own.
Sleep itself adds another layer. The combination of lying down (which can allow mucus to pool in the airways), reduced breathing drive during sleep, and the circadian dip in lung function creates what researchers describe as additive effects. Your airway resistance may be significantly worse at night, but you’re generally unaware of it unless it becomes severe enough to wake you up. This means nighttime attacks often feel sudden and intense, even though the narrowing has been building for hours.
The Role of Eosinophils in Severe Attacks
Not all asthma is the same. In roughly half of people with asthma, the airways contain elevated levels of eosinophils, a type of white blood cell that drives a particularly aggressive form of inflammation. People with high eosinophil counts tend to have a distinct pattern: more frequent severe attacks, worse day-to-day symptom control, and a poorer long-term outlook compared to people whose asthma follows other inflammatory pathways.
The persistent inflammation from eosinophils traps air in the lungs, worsens symptoms between attacks, and over time can cause permanent structural changes to the airway walls (a process called remodeling). This type of asthma often develops in adulthood and tends to respond well to newer targeted treatments that specifically reduce eosinophil activity, which is why identifying this pattern matters for treatment decisions.
Why Some People Develop Asthma
The triggers above explain what sets off an individual attack, but the deeper question is why some people’s airways overreact in the first place. Genetics play a significant role: asthma runs in families, particularly when combined with a tendency toward allergies.
Environment during early childhood also shapes risk. The hygiene hypothesis, supported by epidemiological evidence, suggests that growing up in an extremely clean environment may actually backfire. A newborn’s immune system needs exposure to common bacteria and other microbes to learn which threats deserve a response and which don’t. In very clean households, the immune system misses this education and is more likely to overreact to harmless substances later. Studies have found that asthma and allergic diseases are more common in homes with low levels of bacterial molecules that normally help train the immune system during infancy. Children who grow up on farms, around animals, or in larger families with more germ exposure tend to develop asthma less often.
Early Warning Signs Before an Attack
Most asthma attacks don’t come out of nowhere. Common early signals include increased coughing (especially at night), mild chest tightness, feeling winded during activities that are usually easy, and needing your quick-relief inhaler more often than usual. If you use a peak flow meter, readings dropping to 50% to 79% of your personal best indicate you’re entering what asthma action plans call the “yellow zone,” where your airways are already narrowing and you need to adjust your response before things escalate.
Recognizing these early signs gives you a window to act. Many severe attacks could be prevented or blunted by responding during this phase rather than waiting until breathing becomes severely restricted.