An allergen is anything someone has an allergic reaction to. This reaction may include:1
- Sneezing
- Nasal congestion
- Coughing
- Itching
- Watery eyes
- Rash
There are many environmental allergens found indoors and outdoors. The most common environmental allergies include:1-4
- Pollen (grasses, trees, weeds)
- Mold
- Dust
- Household insects (dust mites, cockroaches)
- Pets (cats, dogs, horses)
People with environmental allergies may also be sensitive to:2-4
- Smoke, fumes, vehicle exhaust
- Strong smells from perfume, hair spray, fumes, air fresheners
- Cleaning products and pool chlorine
- Air pollution (ozone)
Two out of 3 people with asthma also have environmental allergies.1
Pollen allergies
Pollen is a fine, yellow powder that fertilizes plants. It moves from plant to plant by wind, birds, insects, and other animals. Most pollen allergies are caused by grasses, trees, and ragweed, which produce pollen light enough to be carried by the wind.5,6
A pollen count measures how much pollen is in the air. It may be reported with weather forecasts during allergy season. Pollen and air quality counts can be found on many websites and smartphone apps.6
Although it may not always be entirely accurate, it can give you an idea of whether your symptoms might be better or worse that day. It is also important to know what kinds of pollen are high on that day. A high overall pollen count may not affect you if it is not the specific pollen to which you are allergic.6
Mold allergies
There are about 1,000 species of mold in the United States, and many cannot be seen by the naked eye. It is found indoors and outdoors. Mold and mildew are fungi. The seeds are called spores, and they travel through the air. This is what causes allergies.7,8
Some spores spread in dry and windy weather, while others spread through dew or fog in high humidity. Outdoors, mold may live on rotting plant matter. Indoors, mold thrives in damp spots like the bathroom, basement, or kitchen.7
While there are many kinds of mold, only a few dozen cause allergies. Stachybotrys chartarum, also called Stachybotrys atra, alternaria alternata, and cladosporium, are some of the most common molds people react to.8
Dust allergies
Household dust is made of many things, like dirt and pollen you track in from outside, soot, pet dander and hair, dust mites, and clothes fibers.9,10
For people sensitive to dust, allergy symptoms may be worse during or soon after vacuuming, sweeping, and dusting. A dust allergy is closely linked to dust mite allergies.9,10
Dust mite allergies
It is thought that up to half of people with asthma are sensitive to dust mites, and up to 2 out of every 100 people worldwide react to dust mites.11
Dust mites are spider-like bugs that live indoors. They love humidity and feed off of tiny flakes of skin that humans shed every day. The skin flakes often get into inner layers of furniture, bedding, stuffed toys, and carpets – all the places where dust mites live. People can be allergic to both the dust mite and their waste.4,12
It is important to remember that dust mites are present in every home, no matter how clean it is.
Pet allergies
Allergies to pets with fur are fairly common, especially in people who have asthma or other kinds of allergies. With a pet allergy, a person’s immune system reacts to what are normally harmless proteins in the pet’s urine, saliva, or dander (dead skin cells). The pet hair itself is not an allergen. But the fur can trap dander, urine, or saliva, plus other allergens like pollen or dust.13
Up to 3 in 10 people with allergies also have allergic reactions to cats and dogs. Cat allergies are twice as common as dog allergies.13
Cockroach allergies
Cockroaches are insects that contain a protein that many people are allergic to. They gravitate to warm places with food and water, especially inside buildings. Their protein is found in their body, waste, and saliva. Even when dead, cockroaches can still trigger allergies and asthma attacks.14
Smoke, fragrance, and fume allergies
Fragrances can trigger non-allergic rhinitis and asthma. These chemicals may be found in cosmetics, perfumes, air fresheners, cleaning products, and pesticides. This sensitivity can cause headaches, breathing problems, asthma attacks, and skin irritation.15
Exhaust and air pollution can trigger reactions, especially diesel exhaust. One study found air pollution caused by diesel exhaust triggered coughing, wheezing, and shortness of breath because it irritates the lungs. This is especially troublesome for the young, older people, and those with asthma.16
