Air Quality (AQI) and Allergies
Air quality affects allergy and asthma symptoms because pollutants like ground-level ozone and particle pollution irritate already-inflamed airways, and poor-air days can make pollen exposure feel worse. The Air Quality Index (AQI) is the EPA's daily 0–500 scale for outdoor air, color-coded from green (Good) to maroon (Hazardous), with 101–150 (orange) flagged as “Unhealthy for Sensitive Groups” — a category that includes people with asthma and respiratory allergies. Checking the AQI helps you plan outdoor activity and know when to limit time outside.
Quick answer
Air quality affects allergy and asthma symptoms because pollutants like ground-level ozone and particle pollution irritate already-inflamed airways. The Air Quality Index (AQI) is the EPA's daily 0–500 scale for outdoor air, color-coded from green (Good) to maroon (Hazardous), with 101–150 (orange) flagged “Unhealthy for Sensitive Groups” — which includes people with asthma and respiratory allergies. Checking the AQI helps you plan outdoor activity and know when to stay in.
What you need to know
- Air pollutants like ground-level ozone and particle pollution can irritate inflamed airways and worsen allergy and asthma symptoms.
- The Air Quality Index (AQI) is the EPA's daily 0–500 scale reporting outdoor air quality, available free at AirNow.gov.
- AQI is color-coded: green (Good, 0–50), yellow (Moderate, 51–100), orange (Unhealthy for Sensitive Groups, 101–150), red (Unhealthy, 151–200), purple (Very Unhealthy, 201–300), and maroon (Hazardous, 301+).
- People with asthma and respiratory allergies are among the “sensitive groups” who may feel effects starting in the orange (101–150) range.
- The AQI covers outdoor pollutants (ozone, particle pollution, and others) — it doesn't measure pollen or indoor air, though bad-air days can compound pollen symptoms.
- On poor-air days, limiting strenuous outdoor activity and keeping indoor air filtered can reduce symptoms.
How Air Quality Affects Allergies and Asthma
If you have respiratory allergies or asthma, your airways are already prone to inflammation, and air pollution adds another irritant on top. The two pollutants that pose the greatest health threat are ground-level ozone and particle pollution (tiny airborne particles). Both can inflame and irritate the airways, which can worsen coughing, wheezing, and congestion, and can make a day of high pollen feel even harder to tolerate. Poor air quality doesn't cause an allergy, but it can amplify the symptoms you already get.
What the AQI Measures
The Air Quality Index (AQI) is the U.S. EPA's standardized way of reporting daily outdoor air quality on a scale from 0 to 500. It covers five major regulated pollutants — ground-level ozone, particle pollution (PM2.5 and PM10), carbon monoxide, nitrogen dioxide, and sulfur dioxide — and you can check your local AQI for free at AirNow.gov. One important limitation: the AQI reports outdoor air pollution, not pollen counts or indoor air, so on a high-pollen day you may want to check both a pollen forecast and the AQI.
The AQI Color Scale
| Color | Category | AQI range | What it means for sensitive groups |
|---|---|---|---|
| Green | Good | 0–50 | Little or no risk |
| Yellow | Moderate | 51–100 | Acceptable; unusually sensitive people may have mild effects |
| Orange | Unhealthy for Sensitive Groups | 101–150 | People with asthma or respiratory allergies may start to feel effects |
| Red | Unhealthy | 151–200 | Sensitive groups feel more serious effects; general public may feel some |
| Purple | Very Unhealthy | 201–300 | Health alert — increased risk for everyone |
| Maroon | Hazardous | 301+ | Emergency conditions; everyone at higher risk |
People with asthma and respiratory allergies fall into the "sensitive groups," so the orange category (101–150) is a useful signal to start taking precautions.
Planning Around Bad-Air Days
- Check your local AQI (and a pollen forecast) before planning outdoor exercise or long stretches outside
- On orange-or-worse days, reduce strenuous outdoor activity, especially if you have asthma
- Keep windows closed and rely on filtered indoor air when outdoor air quality is poor
- Keep asthma controller medicines and your reliever inhaler on hand and follow your action plan
- Ozone is often highest on hot, sunny afternoons; scheduling activity for cooler parts of the day can help
For reducing indoor triggers on those days, see our air purifiers for allergies and indoor allergens guides. If you have asthma, our allergic asthma management guide covers action plans.
When to seek care
Routine
You want to plan outdoor activity around air quality to reduce allergy or asthma symptoms.
Prompt (within days)
Symptoms that flare noticeably on poor-air days despite precautions — discuss a management plan with a clinician.
Urgent (same day)
Worsening breathing symptoms on a bad-air day, especially with asthma, that your usual medicines aren't controlling.
Emergency (call 911)
Severe shortness of breath, chest tightness, or an asthma attack not responding to your reliever inhaler — call 911.
Practical next steps
Safe general steps
- Check your local AQI at AirNow.gov, plus a pollen forecast, before outdoor plans
- Cut back on strenuous outdoor activity when the AQI is orange or worse
- Keep windows closed and use filtered indoor air on poor-air days
- Keep asthma medicines accessible and follow your action plan
Actions that need medical guidance
- Building an asthma action plan for poor-air-quality days
- Adjusting medications during wildfire smoke or high-pollution periods
- Persistent symptoms that flare with air quality
Don't attempt without professional advice
- Don't do strenuous outdoor exercise on unhealthy-air days if you have asthma or respiratory allergies
- Don't assume the AQI reflects pollen — check a pollen forecast separately
- Don't ignore worsening breathing on a bad-air day — follow your asthma action plan
Frequently asked questions
Does air quality affect allergies?
What is the Air Quality Index (AQI)?
What AQI level is bad for allergies and asthma?
Does the AQI measure pollen?
What should I do on a poor-air-quality day?
What do the AQI colors mean?
Sources
- AirNow.gov (U.S. EPA) — AQI Basics
- AirNow.gov (U.S. EPA) — Air Quality and Health
- AirNow.gov (U.S. EPA) — Using the Air Quality Index
Medical disclaimer: This guide is for general education and isn't a substitute for personalized medical advice. It doesn't provide dosing. Always talk to a qualified healthcare professional about your symptoms and treatment.
MDMedically reviewed
Dr. Hannah H. Walford, MD
Allergist and Immunologist
- Website role
- Owner, Medical Director and Medical Reviewer of Allergy Relief Guide
- Professional affiliation
- Stanford Health Care / Menlo Medical Clinic, Menlo Park, California
- Areas of expertise
- Food allergy, eczema, allergic rhinitis, sinusitis and asthma
Dr. Hannah H. Walford is a board-certified allergist and immunologist experienced in caring for adults and children with allergic conditions. Her areas of expertise include food allergy, eczema, allergic rhinitis, sinusitis and asthma. She provides medical leadership and review oversight for the educational health content published by Allergy Relief Guide.
Medical content is provided for education and is not a substitute for diagnosis or individualized medical care.
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