Physician Specialist Glossary

What Is an Allergy?

Allergies are an abnormal response of the immune system. People who have allergies have an immune system that reacts to a usually harmless substance in the environment. This substance (pollen, mold, and animal dander, for example) is called an allergen.

Allergies are a very common problem, affecting at least two out of every 10 Americans.

What Happens During an Allergic Reaction?

First, a person is exposed to an allergen by inhaling it, swallowing it, or getting it on or under their skin. After a person is exposed to the allergen, a series of events create the allergic reaction:

1. The body starts to produce a specific type of antibody, called IgE, to bind the allergen.
2. The antibodies attach to a form of blood cell called a mast cell. Mast cells can be found in the airways, in the intestines, and elsewhere. The presence of mast cells in the airways and GI tract makes these areas more susceptible to allergen exposure.
3. The allergens bind to the IgE, which is attached to the mast cell. This causes the mast cells to release a variety of chemicals into the blood. Histamine, the main chemical, causes most of the symptoms of an allergic reaction.

Asthma is characterized by inflammation of the bronchial tubes with increased production of sticky secretions inside the tubes. People with asthma experience symptoms when the airways tighten, inflame, or fill with mucus. Common asthma symptoms include:

• Coughing, especially at night
• Wheezing
• Shortness of breath
• Chest tightness, pain, or pressure

Still, not every person with asthma has the same symptoms in the same way. You may not have all of these symptoms, or you may have different symptoms at different times. Your asthma symptoms may also vary from one asthma attack to the next, being mild during one and severe during another.

Some people with asthma may go for extended periods without having any symptoms, interrupted by periodic worsening of their symptoms called asthma attacks. Others might have asthma symptoms every day. In addition, some people may only have asthma during exercise or asthma with viral infections like colds.

Mild asthma attacks are generally more common. Usually, the airways open up within a few minutes to a few hours. Severe attacks are less common but last longer and require immediate medical help. It is important to recognize and treat even mild asthma symptoms to help you prevent severe episodes and keep asthma under better control. 

Know the Early Symptoms of Asthma

Early warning signs are changes that happen just before or at the very beginning of an asthma attack. These signs may start before the well-known symptoms of asthma and are the earliest signs that your asthma is worsening.

In general, these signs are not severe enough to stop you from going about your daily activities. But by recognizing these signs, you can stop an asthma attack or prevent one from getting worse. Early warning signs of asthma include:

• Frequent cough, especially at night
• Losing your breath easily or shortness of breath
• Feeling very tired or weak when exercising
• Wheezing or coughing after exercise
• Feeling tired, easily upset, grouchy, or moody
• Decreases or changes in lung function as measured on a peak flow meter
• Signs of a cold or allergies (sneezing, runny nose, cough, nasal congestion, sore throat, and headache)
• Trouble sleeping

If you have early warning signs or symptoms of asthma, you should take more asthma medication as described in your asthma action plan.