The respiratory system delivers oxygen to your blood and removes carbon dioxide. When the airways narrow, swell, or become blocked by mucus or fluid, breathing becomes difficult. Respiratory conditions fall into three main types, each with distinct causes but overlapping symptoms.
What is asthma?
Asthma is a chronic inflammatory disease of the airways marked by reversible airflow obstruction. During an attack, the muscles around the airways tighten, the lining swells, and mucus builds up, narrowing the passages. Crucially, this narrowing is reversible. The airway reopens with treatment, distinguishing asthma from COPD, in which damage is often permanent.
Asthma affects roughly 8% of U.S. adults and 7% of children, and it can develop at any age, though childhood-onset is most common. It comes in several forms: allergic asthma (triggered by pollen, dust mites, dander, or mold) is the most common, while exercise-induced, occupational, eosinophilic (which often needs biologic therapy), cough-variant, and aspirin-exacerbated forms each have distinct triggers.
The term “reactive airway disease” is sometimes used loosely to refer to asthma, so ask your provider what your specific diagnosis means.
What is COPD?
Chronic obstructive pulmonary disease (COPD) is a group of progressive lung diseases marked by persistent airflow limitation that, unlike asthma, is not fully reversible. It mainly includes chronic bronchitis (long-term airway inflammation) and emphysema (destruction of the lung’s air sacs), and most people with COPD have features of both.
COPD affects roughly 6% of U.S. adults, about 16 million people, and is a leading cause of death. Smoking is the primary cause, though non-smokers can develop it from occupational or environmental exposure to dust, chemicals, or air pollution.
Severity is graded from GOLD Stage 1 (mild) to Stage 4 (very severe) based on spirometry, and emphysema and chronic bronchitis are components of COPD rather than separate diagnoses.
What are allergies?
Allergies are an overreaction of the immune system to a normally harmless substance. On exposure, the immune system releases histamine and other chemicals, triggering inflammation in the nose, sinuses, airways, skin, or digestive tract.
Allergies affect roughly 50 million Americans a year and, while not always serious, can significantly affect quality of life and, in severe cases (anaphylaxis), become emergencies. They take several forms: seasonal allergies (hay fever) from tree, grass, and ragweed pollen; perennial allergies from year-round indoor triggers like dust mites, pet dander, and mold; food allergies; and environmental reactions to pollution or smoke.
Unlike a cold, which is viral and typically resolves in 7 to 10 days with yellow-green mucus, allergies persist with continued allergen exposure and tend to cause clear discharge and itching.
Asthma vs. COPD vs. allergies at a glance
|
Asthma |
COPD |
Allergies |
| Typical onset |
Any age; often childhood |
Usually, after age 40 |
Often childhood/adolescence |
| Airflow obstruction |
Reversible |
Not fully reversible |
Not a core feature |
| Main cause |
Genetics + triggers |
Smoking, exposures |
Immune (IgE) response |
| Hallmark symptom |
Episodic wheeze, cough |
Progressive breathlessness |
Sneezing, congestion, itch |
| First-line treatment |
Inhaled corticosteroids |
Long-acting inhalers |
Antihistamines, avoidance |