Asthma

What Is Asthma?

For lots of people—maybe even you—asthma is a fact of life. One in every fifteen Americans suffers from asthma. And nearly five million of those are under age eighteen.

People are diagnosed with asthma at every stage of life—from infants to teens to the elderly. Sometimes people live with asthma throughout their lives. Other times young people outgrow the condition by the time they reach adulthood. Some infants outgrow asthma by early childhood. But no matter who you are, and when you develop asthma, it’s always treatable. With proper treatment and the right information, asthma can be managed, and you can live a healthy life.

Asthma Defined

First things first: You’re probably asking yourself, what exactly IS asthma? Asthma is a chronic condition that affects the lungs and bronchial tubes and impairs the ability to breathe. Scientists believe that asthma is likely an inherited condition, caused by one or more genes. A gene is a part of your DNA that controls the physical traits you inherit from your parents. The fact that children born into families with a history of asthma have a greater likelihood of developing asthma themselves supports this theory. Many scientists also think that environmental factors (like living in an urban area with lots of dust) can help trigger asthma.

The Respiratory System

Respiratory SystemView Larger Image

To understand asthma, first you have to understand how the respiratory system works. Think of a person’s airway as an upside-down tree. The windpipe (called the trachea) is like the trunk of the tree. The bronchial tubes extend into the right and left lungs and represent the tree’s largest branches. The bronchioles are narrower tubes that branch off the bronchial tubes, like smaller branches of the tree.

Now let’s add more detail to the tree: The alveoli are the smallest parts of the lungs (the air sacs) where the exchange of oxygen and carbon dioxide takes place. The alveoli are like leaves on a branch and are surrounded by millions of tiny blood vessels. Small blood vessels called capillaries take the oxygen you breathe from the alveoli and transfer it to larger blood vessels (pulmonary veins). This oxygenated blood is pumped back into the heart and then distributed throughout the rest of the body. At the same time, the tiny blood vessels exchange the used air (carbon dioxide) for fresh, oxygenated air. Then the carbon dioxide is expelled when you exhale. You wouldn’t survive for long if you weren’t able to get rid of the carbon dioxide in your blood.

Here’s where the muscles come in. The trachea (or windpipe) is the long tube extending from the back of the throat to the entrance of the lungs. The trachea is made up of bands of muscle and cartilage. Muscle can do two things: tighten (constrict) or relax and open up (dilate). Ordinarily, when you take a breath, the air moves through the mouth or nose and travels down the windpipe to the bronchial tubes. Eventually, after being exchanged across the alveoli, the inhaled oxygen is added to the blood. This is how your body obtains the oxygen it needs to survive.

When a person has asthma, however, the trachea and bronchial tubes are overly sensitive. When irritated, the muscles and the lining constrict more easily and make it difficult to breathe. This phenomenon is called an asthma attack. If you’ve ever had an attack, you know what this feels like.

Several things can trigger an asthma attack. The most common triggers are allergens (substances that cause an allergic reaction). People with asthma have bronchial tubes that are far more sensitive to allergens and irritants in the air than people who don’t have asthma. When an allergen enters the body, the bronchioles can sometimes overreact. Tissues in the airway swell up, and the production of mucus increases. The flow of air in and out of the lungs is decreased or even blocked. If you’ve suffered an asthma attack, you may have felt as if an invisible hand were tightly squeezing your windpipe or chest.

What Triggers an Asthma Attack?

Unlike many lung conditions, asthma is episodic, meaning it comes and goes. People have asthma attacks, recover, and then at a later point might suffer another attack. Some people have attacks very frequently, even multiple times a day, while other people might go for months before suffering another attack.

To understand asthma, you need to know how an attack occurs in the body. There are three main components: The immune system, histamine, and allergens/irritants.

The Immune System

Of course, you’ve probably heard about the immune system before. It protects the body from harmful foreign invaders, such as viruses, bacteria, and germs. But did you know that the immune system plays a big role in the development of asthma? Sometimes, for unknown reasons, the immune system reacts to harmless substances that enter the body. This reaction is known as an allergy.

Scientists believe some people develop asthma because of allergic reactions to substances like pollen, mold spores, certain types of food, and animal dander. Although these substances in themselves pose no threat to the average person, they can cause an asthma attack in a “susceptible person.”

Histamine

Now that you know more about the immune system, you need to know how histamine acts in your body. When an allergen (substance that causes an allergic reaction) enters the body, it reacts with immunoglobulin E (IgE). IgE is found on the surface of certain circulating white blood cells called basophils and on mast cells (a type of cell that lines the walls of the nose, bronchial tubes, intestines, and skin). When IgE detects an allergen, the basophils and mast cells react to the allergen by releasing histamine to fight off the invader. Histamine is an inflammatory chemical released by your immune system during an allergic reaction. It causes the surrounding tissues to become inflamed and swollen.

If you’ve ever had an asthma attack or an allergic reaction, you’re probably familiar with what histamine can do. Once released in the lungs, histamine causes a number of reactions. Mucus is secreted in the lungs and the linings of airways narrow and swell. This causes a person to wheeze, become short of breath, and cough. As these reactions worsen, they can develop into an asthma attack.

Common Allergens and Irritants

Among the common allergens and irritants that can provoke an asthma attack are:

• Mold and dust. Both mold and dust are powerful, hard-to-eliminate allergens. Mold isn’t just the green substance you see on aging bread and cheese. It’s present in house plants, shower stalls, curtains, and humidifiers. Many molds are microscopic and cannot be seen by the naked eye.

  Dust is made up of some unpleasant potential allergens: Pollen, food particles, mite (a tiny creature that lives in dust) and cockroach feces and body parts, animal dander, and dead human skin cells. In fact, many scientists believe that the rise in asthma among urban youth is due to cockroaches and other bugs in inner-city apartments.

• Smoke. Tobacco and wood smoke can trigger the body’s production of histamine. And you don’t have to be a smoker to feel its effects. Second-hand smoke (what you breathe when other people are smoking around you) is still toxic. Studies show that exposure to secondhand smoke can make the lungs more susceptible to asthma triggers, and that it can worsen asthma attacks in those who suffer from them.

• Food. Common food allergens are nuts, milk products, and shellfish. Food allergens can be particularly dangerous because they often lead to asthma attacks very quickly. In rare cases, they can cause anaphylaxis (swelling of the throat and difficulty breathing).

• Pets. Animals’ dead skin cells are called dander. When an animal sheds these cells, they float in the air. Dander is easily airborne and when inhaled, causes asthma symptoms to flare up. The irritating effects linger long after the pet has gone, which is why someone can suffer an asthma attack long after an animal has left a room. Cat dander is the smallest and strongest pet-related airborne allergen—more so than the hair or fur itself!

• Odors and fumes. Scented products such as air fresheners, perfumes, cosmetics, and cleaning solutions can trigger asthma symptoms, as can strong odors from fresh paint, insecticide, or gasoline fumes. When these odors are inhaled, they irritate the lungs and can cause an asthma attack.

Other Asthma Triggers

• Exercise. Strenuous sports can trigger an asthma attack, especially those that involve a lot of running, such as track or soccer.

• Weather. Some people develop asthma symptoms in certain weather conditions, such as hot and humid air, in smog (a thick haze), or on cold, windy days.

• Infections. Respiratory infections, such as a cold or bronchitis, can contribute to the onset of asthma attacks.

One of the most important parts of controlling asthma is learning what triggers your attacks. When you know what causes an attack, you can make smart choices and avoid putting yourself in uncomfortable or dangerous situations.