Allergens and Allergic Asthma

What Is an Allergen?

Allergens are substances that cause an allergic reaction. Allergens can enter the body by being inhaled, swallowed, touched or injected.

What Is Allergic Asthma?

More than 25 million people in the US have asthma, and allergic asthma is the most common type, affecting around 60% of people with asthma. Both allergic and non-allergic asthma have the same symptoms, such as shortness of breath and wheezing.

Having allergic asthma means allergens trigger your asthma symptoms. Allergens cause an allergic reaction because your immune system thinks they are harmful. Your immune system responds by releasing a substance called immunoglobulin E (or IgE). Too much IgE can trigger inflammation (swelling) of the airways in your lungs. This can make it harder for you to breathe and can trigger an asthma attack.

How Do I Know If I Have Allergic Asthma?

Only a doctor can confirm a diagnosis of allergic asthma. This is usually done using a skin or blood test. These tests will help determine if seasonal allergies or year round allergies trigger your asthma.

What Are the Common Triggers of Allergic Asthma?

Learning to avoid your allergens is key to managing your allergic asthma. Find out how to avoid these common allergens:


These insects live all over the world from tropical areas to the coldest spots on earth. Studies show most urban homes have cockroaches. The feces, saliva and body parts of these insects are believed to be allergens.

Dust Mites  

These spider-like creatures are too small to see with the naked eye. They feed on human skin flakes. Both the body parts and feces of dust mites are considered allergens. They are found in mattresses, pillows, carpets, upholstered furniture, bedcovers, clothes, stuffed toys, fabric, etc.


Molds can grow on almost anything when moisture is present. Outdoors, many molds live in soil, or on leaves, wood, and other plant debris. Indoors, they can be found in a damp basement, near a leaky faucet or pipe, or a wet shower stall or bathtub. Molds produce tiny spores, which are like seeds, to reproduce. These spores become airborne easily.


Pet urine, feces, saliva, hair or dander (skin flakes) are all allergens. But you don't have to have pets in your house or visit places where animals are kept in order to be exposed to their allergens. Animal allergens are often detected in places where no animals live. People who own or have been around animals may have carried the allergens into the place.


Pollen from trees, grasses and weeds is a common allergen. These airborne particles often peak during different seasons of the year, but they can linger in your home and air ducts all year long. 

Medical Review September 2015.