What causes asthma?

Our bodies need oxygen from the air we breath in order for our cells to do their work. Asthma attacks can be very frightening and there is often panic. Although there are varying degrees of the disease, it can be life threatening. When we breath in, air, containing oxygen, enters through the mouth or nose, and descends through the windpipe, to tubes called the bronchi. The bronchi branch out into each lung where oxygen is picked up by passing blood. The blood then carries the oxygen throughout the body.

For a variety of reasons, what happens during an asthma episode is that the bronchial tubes become narrow, or even blocked. As a result, air can’t get in or out of the lungs easily, and the child begins to breathe heavily, wheeze or cough.

There are two reasons the bronchi narrow: Either because they are squeezed by muscles from the outside or because they are blocked by mucus and swelling inside the bronchial tubes.

Bronchoconstriction

The condition when bronchi are narrowed by squeezing, is called “Bronchoconstriction.” This occurs when muscles, wrapped around the bronchi like a series of elastic bands, tighten and restrict the passage of air. It’s normal for these muscles to occasionally close the airway. But in asthmatics these muscles sometimes overreact, become twitchy and constrict or block the bronchi.

Inflammation

For many years, bronchoconstriction was thought to be the main cause of asthma. More recently, we’ve become aware of another problem: Bronchial Inflammation. This occurs when the walls of the bronchi swell up and produce mucus, in reaction to some sort of irritation.

It’s normal for the bronchi to produce mucus in order to trap breathed-in irritants, and protect the lungs. But some asthmatics can produce an overabundance of mucus, and the bronchi can become chronically inflamed,

resulting in blocked airways and asthmatic symptoms.

So there are two possible conditions associated with an asthmatic’s airways, bronchoconstriction and bronchial inflammation. In fact it is widely believed that the more an airway is inflamed, the more likely it is that the bronchial muscles will constrict.

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All of us have heard of asthma and know that it is something to do with difficulty breathing, but unless you have experienced it first hand in yourself or with your child, you have no idea of the terror this condition can bestow. Asthma attacks can be very frightening and there is often panic. Although there are varying degrees of the disease, it can be life threatening. If you or a family member has asthma, prepare an emergency plan ahead of time. If the attacks are usually mild, you may have a routine of medications, such as an inhaler that is kept on the person at all times. For a more serious attack, however, have a plan of action. Talk to your doctor about keeping an injectable bronchodilator in the house. Have emergency call numbers posted by and/or on the phone itself. Talk to all members, even younger members of the family and explain to them about calling 911 for emergencies, like when “Johnny” is having trouble breathing.

Now let’s talk about this terrential disease, asthma, in more detail. Asthma is a disease that effects the bronchial tubes. It is a direct result of allergies. Asthma is a very scary thing for any person, especially a young child. The bronchial tubes of people with asthma are very sensitive to substances that they are allergic to. These irritants cause the bronchial tubes to swell. Asthma has exacerbations or “attacks”, as most people call them. An asthma attack can occur when someone is exposed to the irritants they are highly allergic to. As of yet, there is no cure for asthma, but doctors are learning more about it. Most persons develop asthma in childhood, but some people develop asthma as adults. It usually gets progressively worse in adults, leading to emphysema. About one in four persons who develop the disease in childhood will have a spontaneous recovery.

The symptoms include: wheezing, coughing, shortness of breath, and tightness of the chest, the person may turn bluish in color and after have weakness, rapid pulse and even nausea and chest pain. Things that can cause an asthma attack, depending on the person, as different people are allergic to different things, include, but are not limited to:
-certain foods

-certain medicines

-air pollution

-smoke

-molds

-perfumes

-dust

-fumes

-additives and preservatives in certain foods such as wine, salad dressings, beer, dehydrated soups.

-hair spray, spray deoderants

-pollen

other things such as:

-emotional stress

-exercise

-temperature changes

-medications

-sinus and other infections

Asthma causes

Treatment and care of asthma is directed toward immediate relief of the attack. Parents of asthmatic children may anticipate an approaching attack and medication that provides sedation and bronchodilation. The control of asthma depends on finding the cause and eliminating it. No smoking for adults who have asthma. There are two kinds of asthma medicines: those that relieve airway constriction and those that reduce swelling and inflammation like steroids. They are usually given via inhalers but pills are used as well. In some cases, studies have shown that coffee, can help relieve an acute asthma attack, supposedly because of the caffiene and heat.

A peak flow meter is an instrument needed by asthmatics. Your doctor can give you one. It is a simple hand held device that is an important part of controlling asthma. It measures the rate of air exhaled from the lungs. You take a deep breath, then blow into it. It records a number. Do it three times. Whatever your best score was, is YOUR peak flow personal best number. Do it everyday for a couple of weeks to make sure you have YOUR personal best right. After you know your best number, let your doctor know. This will help him treat YOUR asthma best.

An asthma attack is very scary, especially for a child. Try to keep them calm and stay with them. If an asthma attack is severe, 911 should be activated and hospitalization is sometimes required. Reducing exposure to allergens and keeping the person calm and limit exposure to drastic temperature changes and avoid foods that the person is allergic to.

Ways to reduce exposure to allergens that can precipitate asthma attacks are:

-Clean carpets

-wash pillowcases and sheets in hot water weekly

-wash your hands regularly to avoid exposure to illness

-remove rugs, carpets and drapes which collect dust

-keep your windows closed

-keep air conditioning on, but make sure your ducts and filters are kept clean

-keep animals outside

What Causes Asthma

Since asthma has a genetic origin and is a disease you are born with, passed down from generation to generation, the question isn’t really “what causes asthma,” but rather “what causes asthma symptoms to appear?” People with asthma have inflamed airways which are super-sensitive to things which do not bother other people. These things are called “triggers.”

Although asthma triggers vary from person to person based on if you have allergic asthma or non-allergic asthma, some of the most common include:

Substances that cause allergies (allergens) such as dust mites, pollens, molds, pet dander, and even cockroach droppings. In many people with asthma, the same substances that cause allergy symptoms can also trigger an asthma episode. These allergens may be things that you inhale, such as pollen or dust, or things that you eat, such as shellfish. It is best to avoid or limit your exposure to known allergens in order to prevent asthma symptoms.

Irritants in the air, including smoke from cigarettes, wood fires, or charcoal grills. Also, strong fumes or odors like household sprays, paint, gasoline, perfumes, and scented soaps. Although people are not actually allergic to these particles, they can aggravate inflamed, sensitive airways. Today most people are aware that smoking can lead to cancer and heart disease. What you may not be aware of, though, is that smoking is also a risk factor for asthma in children, and a common trigger of asthma symptoms for all ages. It may seem obvious that people with asthma should not smoke, but they should also avoid the smoke from others’ cigarettes. This “secondhand” smoke, or “passive smoking,” can trigger asthma symptoms in people with the disease. Studies have shown a clear link between secondhand smoke and asthma, especially in young people. Passive smoking worsens asthma in children and teens and may cause up to 26,000 new cases of asthma each year.

Respiratory infections such as colds, flu, sore throats, and sinus infections. These are the number one asthma trigger in children.

Exercise and other activities that make you breathe harder. Exercise—especially in cold air—is a frequent asthma trigger. A form of asthma called exercise-induced asthma is triggered by physical activity. Symptoms of this kind of asthma may not appear until after several minutes of sustained exercise. (When symptoms appear sooner than this, it usually means that the person needs to adjust his or her treatment.) The kind of physical activities that can bring on asthma symptoms include not only exercise, but also laughing, crying, holding one’s breath, and hyperventilating (rapid, shallow breathing). The symptoms of exercise-induced asthma usually go away within a few hours. With proper treatment, a child with exercise-induced asthma does not need to limit his or her overall physical activity. (See the page on Exercise-Induced Asthma .)

Weather such as dry wind, cold air, or sudden changes in weather can sometimes bring on an asthma episode.

Expressing strong emotions like anger, fear or excitement. When you experience strong emotions, your breathing changes — even if you don’t have asthma. When a person with asthma laughs, yells, or cries hard, natural airway changes may cause wheezing or other asthma symptoms.

Some medications like aspirin can also be related to episodes in adults who are sensitive to aspirin. Irritants in the environment can also bring on an asthma episode. These irritants may include paint fumes, smog, aerosol sprays and even perfume.
People with asthma react in various ways to these factors. Some react to only a few, others to many. Some people get asthma symptoms only when they are exposed to more than one factor or trigger at the same time. Others have more severe episodes in response to multiple factors or triggers. In addition, asthma episodes do not always occur right after a person is exposed to a trigger. Depending on the type of trigger and how sensitive a person is to it, asthma episodes may be delayed.

Each case of asthma is unique. If you have asthma, it is important to keep track of the factors or triggers that you know provoke asthma episodes. Because the symptoms do not always occur right after exposure, this may take a bit of detective work.

What Happens During an Asthma Episode?

During normal breathing, the airways to the lungs are fully open, allowing air to move in and out freely. But people with asthma have inflamed, super-sensitive airways. Their triggers cause the following airway changes, which in turn cause asthma symptoms:

The lining of the airways swell and become more inflamed
Mucous clogs the airways
Muscles tighten around the airways (bronchospasm)
These changes narrow the airways until breathing becomes difficult and stressful, like trying to breathe through a straw stuffed with cotton.

Why Does My Asthma Act Up at Night?

For reasons we don’t fully understand, uncontrolled asthma — with its underlying inflammation — often acts up at night. It probably has to do with natural body rhythms and changes in your body’s hormones, as well as the fact that some symptoms appear hours after you come in contact with a trigger. The important thing to know about nighttime asthma is that, working with your doctor, you should be able to sleep through the night.

The Role of Heredity in Asthma.

Like baldness, height and eye color, the capacity to have asthma is an inherited characteristic. Yet, although you may be born with the genetic capability to have asthma, asthma symptoms do not automatically appear. We do not know for certain why some people get asthma and others do not. However, doctors doing research have found that certain traits make it more likely that a person will develop asthma.

Heredity. To some extent, asthma seems to run in families. People whose brothers, sisters or parents have asthma are more likely to develop the illness themselves.

Atopy. A person is said to have atopy (or to be atopic) when he or she is prone to have allergies. For reasons that are not fully known, some people seem to inherit a tendency to develop allergies. This is not to say that a parent can pass on a specific type of allergy to a child. In other words, it doesn’t mean that if your mother is allergic to bananas, you will be too. But you may develop allergies to something else, like pollen or mold.
In addition, several factors must be present for asthma symptoms to develop:

Specific genes must be acquired from parents.
Exposure to allergens or triggers to which you have a genetically programmed response.
Environmental factors such as quality of air, exposure to irritants, behavioral factors such as smoking, etc.

What’s causes asthma?

No one knows exactly what causes asthma. It is not even clear whether asthma is one disorder or a group of disorders with similar manifestations. Still, much has been learned about who is most likely to develop asthma and how an asthma attack occurs. To put it simply, a person becomes susceptible to developing asthma because of genes, but develops the disorder only after exposure to things in the environment that stimulate the immune system in such a way that the airways become inflamed and prone to attacks.

A simple example may help explain how genetic and environmental factors can interact to produce asthma. Suppose you inherit a tendency to be allergic to cockroaches. After many years of living in a single-family house, you move to an apartment complex. The good news is that you don’t have to mow the lawn anymore — but you may also find yourself living with cockroaches for the first time in your life. This can lead over time to an allergic irritation of your bronchial tubes. Once irritated or inflamed in this way, your bronchial tubes react not only to cockroaches but also to many other types of stimuli that typically make asthma worse, such as smoke, exercise, and respiratory infections. After many months or years of exposure, even if you move out of the apartment into one that doesn’t have a cockroach problem, this hypersensitivity of your airways — in other words, your asthma — may persist.

It has long been known that people inherit a tendency to develop asthma. The condition tends to run in families; if your brothers, sisters, or parents have asthma, you are more likely to develop it yourself.

The genetic contribution to asthma is far from simple, however. It’s almost certain that a number of genes are responsible for the predisposition to asthma, and that these genes somehow interact to produce the disorder. Yet even if you are born with the genes predisposing you to asthma, you may never go on to develop the disease. This has been shown by studies of identical twins, who share the same genes. When one identical twin develops asthma, there is only a one in three chance that the other twin will develop it as well. Clearly, something in the environment must also be responsible for asthma.

Scores of asthma-related genes have been discovered, and this knowledge is helping to expand avenues of asthma research. Still other asthma genes are thought to exist, and it is unclear yet which ones are most significant. The research in this area continues, with the hope that better understanding of the genetic basis of asthma will lead to better treatments and potentially even a cure.

Asthma – Environmental factors

It is likely that inhaled substances are the most important environmental factors contributing to the development of asthma in people with a genetic predisposition to the disorder. The leading suspects are allergens (substances that cause an allergic reaction; see “The allergy connection”). Other potential culprits include tobacco smoke, air pollution, and infectious agents such as viruses and mycoplasma. Asthma most often develops during childhood following exposure to one or more of these environmental factors, but it can also develop in adulthood.

Adults who smoke, who are exposed to irritating chemicals in the workplace, or who suffer a particularly nasty respiratory infection may develop asthma. A number of specific occupations can expose workers to agents that can trigger asthma (see “Selected causes of occupational asthma”). Hormone replacement therapy in menopausal women is another risk factor: The Nurses’ Health Study, a large epidemiological study that has collected information about women’s health issues since 1976, found that menopausal women who were currently using or who had used estrogen replacement therapy had a 50% greater risk of developing asthma than those who did not take hormones. In addition, a study of more than 2,000 women found that hormone replacement therapy may increase women’s risk of asthma and wheezing, particularly if they are lean. Often, however, there is no identifiable cause of adult-onset asthma. In some cases, the problem may have been present in childhood but was undiagnosed, or it may have been present in childhood, become dormant around adolescence, then resurfaced in adulthood.

The allergy connection

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When most people think of allergies, they’re likely to think of sneezing and a runny or stuffy nose; red, itchy, watery eyes; or perhaps dry, red, itchy skin. But one theory about asthma is that it is also an allergic reaction — in this case, affecting the bronchial tubes.

In fact, allergic rhinitis (allergies of the nose), allergic conjunctivitis (allergies of the lining of the eyes), and allergic dermatitis (allergies of the skin, also called eczema) frequently occur together in various combinations both in individuals and in families, and they often occur together with asthma.

All these conditions share a common mechanism: They result from a specific type of allergic reaction. The tendency to have this specific type of allergic reaction is called atopy, and people who have this tendency are said to be atopic. Asthma accompanied by allergies is often referred to as atopic asthma or extrinsic asthma. The vast majority of children with asthma, and probably at least half of the adults with the disorder, have the atopic variety.

The allergic basis of asthma has provided insight into which proteins and cells are involved in the inflammation of the bronchial tubes. People who have allergies make a special kind of protein, called an antibody, that is precisely shaped to recognize and attach itself firmly to a particular allergen. This antibody belongs to the family of immune defenders called immunoglobulins. The defenders that are specifically designed to recognize allergens are referred to as immunoglobulin E (IgE). Let’s say you are allergic to dust mites; you make IgE antibodies that recognize the dust mite allergen.

The IgE antibodies do not roam freely in your breathing tubes but are firmly attached to immune system cells called mast cells. These cells are located mainly in parts of the body that regularly encounter substances from the outside world: the skin, intestinal tract, lining of the eye (conjunctiva), nose, and breathing tubes.

In people with allergic asthma, the surface of each mast cell is coated with firmly attached IgE antibodies. All remains quiet until the IgE antibodies recognize and attach themselves to an allergen. Then, within seconds, an explosive reaction takes place (see Figure 3). The mast cell makes and releases a barrage of chemicals that carry out the inflammatory reaction. These chemicals include histamine (which you may be aware of if you are familiar with antihistamines for treating allergies), leukotrienes, and many others.

Together these inflammatory chemicals cause blood vessels to leak fluid, producing swelling in the breathing tubes. They stimulate the walls of the breathing tubes to secrete mucus. They also make the muscles surrounding the breathing tubes contract, narrowing these passageways. As if that weren’t enough, mast cells also call in reinforcements, other cells involved in allergic inflammation that travel from the blood to the site of the allergic reaction and make things worse. The most important of these reinforcements are blood cells called eosinophils. Like mast cells, they release chemicals that cause the airways to narrow.

Chronic inflammation
In asthma, the allergic inflammatory process never really stops. An important medical discovery was that some inflammation is present in the bronchial tubes of people with asthma even when they feel well and when their breathing is normal. Medical researchers performed experiments in people with asthma to sample (biopsy) small pieces of the walls of the bronchial tubes. The samples were taken at times when the research participants were free of asthma symptoms. Yet in the biopsied tissues, scientists found evidence of persistent inflammation of the bronchial tubes.

This suggests that airway inflammation in asthma is always present, at least to some degree. The inflammation may be so mild that it does not cause narrowing of the bronchial tubes. But the persistent presence of this inflammation is probably a major reason that the bronchial tubes are twitchy, or capable of narrowing abnormally.

Why is asthma so common?

“Asthma” used to be on the increase in the United States (see “Asthma in America”), but its prevalence has stabilized. Despite this good news, official estimates of asthma prevalence may not truly reflect how many people really have the disease, because studies have shown that there are many people with undiagnosed asthma.

According to the Global Initiative on Asthma, more than 10% of the people in North America, Australia, and much of South America have asthma, compared with fewer than 2.5% in the former Soviet Union and much of Asia. The higher prevalence of asthma in urban versus rural environments, and in westernized versus developing countries, has made researchers wonder if some lifestyle factor has contributed to the dramatic increase of allergies and asthma in the industrialized world. Several hypotheses have been developed, although there remains no consensus about what may have caused the increase.

Air pollution. This would seem an obvious culprit for the increase in asthma in industrialized nations, since air pollution can trigger an asthma attack, but this popular explanation for the increase in asthma does not hold up under close examination. When Germany became a unified country again in 1990, researchers compared asthma prevalence in the former East Germany and West Germany. The expectation was that asthma would be more common among people living in the highly polluted East German cities. In fact, just the opposite was true: Asthma turned out to be more common in West Germany, indicating that something other than air pollution must be responsible.

Increased exposure to allergens. Another theory holds that modern urban life is exposing young children more to common household allergens and making them more susceptible to allergy-related asthma. As a rule, people are much more likely than their parents and grandparents to live in the city and spend much of the time indoors, in close quarters with dust mites, cockroaches, and animal hair (from either pets or pests). Television, computers, and video games have seduced people into staying inside even more. To further complicate matters, home insulation was upgraded in response to the energy crisis of the 1970s, so that houses and apartments today tend to be more tightly sealed. The result is far less circulation of fresh air and greater exposure to higher concentrations of allergens.

The hygiene theory. According to this hypothesis, the immune systems of children who are exposed to lots of important infections and toxins early in life tend to ignore less serious challenges, such as those from allergens like pollen and dog dander. But when children grow up in a germ-free environment, they are exposed to relatively fewer serious infections, and the immune system has more “free time” to direct its attention against harmless allergens. So the good news is that serious infections such as tuberculosis and whooping cough are much less common than they used to be. The bad news, according to the hygiene theory, is that children’s immune systems are more likely to react in a way that causes allergic diseases, including asthma.

Several major medical studies have supported the hygiene hypothesis. For instance, infants who go to day care or have older siblings are less likely to develop asthma later in childhood than those who don’t attend day care or have siblings. Because they are more frequently exposed to other children, the infants who go to day care and have older siblings are naturally exposed to more germs. Similarly, children living in farming communities with close contact with farm animals are less likely than others to develop asthma (and their risk decreases the more they are exposed to toxins from animal droppings). It may be that their developing immune systems learn to focus on germs and toxins and to ignore allergens, thereby decreasing the likelihood of allergies and asthma later in childhood.

Obesity. Yet another theory about the increase in asthma is that it is linked to being overweight. Obesity is common in the United States and has increased since the 1970s. Being overweight raises the risk for heart disease, diabetes, and other diseases. Findings from several studies suggest that asthma can also be added to the list of obesity-related illnesses. In one study, researchers looked at more than 7,000 children, ages 4 to 17, and found that those who were overweight were almost twice as likely to develop asthma as normal-weight children. Another study found that women who are overweight have an increased risk of asthma, wheezing, and allergy. The exact connection between asthma and weight is unknown, but one simple explanation is that excess weight places pressure on the chest, which contributes to constriction of the airways.