Causes of asthma and trigger factors

Questions

What causes asthma?

What causes asthma symptoms or an asthma attack?

What are asthma triggers?

What are the main asthma triggers?

What chemicals; irritants or other substances trigger asthma?

Can medications trigger asthma?

Can weather changes trigger asthma?

Can infections trigger asthma?

Can an allergic reaction trigger asthma?

Is asthma a psychological (psychosomatic) disease?

Why is it sometimes so hard to know what triggers an asthma attack?

Why does my asthma get worse when I am upset or worried about something?

Why do I not react when I meets my neighbour’s dog outdoors, although I react  indoors?

Can I really get asthma symptoms from a plastic Christmas tree?

Answers to your questions

What causes asthma?

The causes of asthma are not fully understood. Its symptoms are caused by inflammation, which makes the airways red, swollen, narrower and extra-sensitive to irritants. Asthma is probably usually caused by a mixture of hereditary factors (those you are born with) and environmental factors, but how these factors work together is still largely unknown.

Allergens from house dust mites and pets are the most common causes, but many other allergens, such as pollen and moulds, can cause asthma. Some people with asthma have no obvious allergies.

What causes asthma symptoms or an asthma attack?

Some causes of symptoms (triggers) are common to all people with asthma, and some are more individual, especially allergens. There are very big differences between people in how easily and how severely they react. The severity of the symptoms or an attack can differ in the same person at different times, and treatment can also be more or less effective.

Your asthma does not stay the same, but changes over time, and every person with asthma has good days and bad days (or longer periods). However, if asthma is properly treated, there can also be long periods without symptoms or attacks.

What are asthma triggers?

Asthma triggers are factors that start asthma symptoms or an asthma attack by irritating the airways or worsening the inflammation in the airways. These triggers can provoke attacks in individuals who already have a tendency to asthma, but they are not necessarily part of the cause of that tendency. The following triggers can cause asthma symptoms or start an asthma attack:

• infections, usually those caused by a virus (e.g. colds or flu) 
• allergens, most commonly from house dust mites, pets or pollen 
• exercise, especially in cold weather 
• emotions, such as excitement, fear or anger 
• irritants, such as air pollution 
• smoking – people with asthma and the parents of asthmatic children should avoid smoking 
• changes in the weather (e.g. a cold spell) 
• food additives, such as tartrazine (an artificial food colouring), or food allergens, such as peanuts (sensitised or allergic individuals can have a very severe allergic reaction). 
• certain medications – some people may be allergic to some drugs (e.g. aspirin).

What are the main asthma triggers?

Different triggers can start an asthma attack and people differ a lot in how easily and how severely they react.
Some triggers (also called ‘inciters’) only cause tightening of the airways (bronchoconstriction) that lasts for just a short time. These triggers include:

• exercise 
• cigarette smoke 
• changes in air temperature 
• laughing 
• strong smells

Other triggers (also called ‘inducers’) also increase the underlying inflammation of the airways, and may have longer-term effects. Such triggers include:

• allergens (e.g. pets, house dust mites and pollen) 
• infections (e.g. colds, flu) 
• certain chemicals

What chemicals, irritants or other substances trigger asthma?

Many irritating particles or chemicals in the air can trigger an asthma attack. Examples include:

• cigarette smoke 
• diesel exhaust 
• perfume or other strong scents 
• household sprays 
• sulphur dioxide '
• grain or flour dust
• sawdust

However, there are very big differences between people in how easily and how severely they react. This depends on the severity of the asthma and how well it is treated.

Can medications trigger asthma?

Only a few medications can trigger asthma. Check with your doctor or pharmacist before starting any new medicine. And if your asthma symptoms are worse after starting a new medication, you should see your doctor immediately.

The most common medicines that can trigger asthma are:

• aspirin (acetylsalicylic acid) and certain other NSAID (non-steroidal anti-inflammatory) drugs, which are used as pain relievers, and to treat arthritis and inflammatory conditions
• beta-blockers, which are used to treat high blood pressure, heart conditions, migraine or anxiety

Not all patients with asthma react to aspirin or NSAIDs, so some people with asthma can use these drugs. However, beta-blockers are likely to cause asthma symptoms in all patients with asthma and should always be avoided.

Can weather changes trigger asthma?

Yes, sudden weather changes (e.g. cold winds, humidity and storms) can trigger asthma in some people. Some of these sudden changes can cause the release of allergens, such as pollen, that can make asthma worse in people whose asthma is allergy-related. Cold air can also have a direct irritant effect on inflamed airways.

Can infections trigger asthma?

Yes, viral respiratory infections, such as colds or flu, can trigger asthma symptoms, particularly in children. Try to avoid contact with people if you know they have a respiratory infection.

Can an allergic reaction trigger asthma?

Yes. Once you are sensitised or allergic, both indoor and outdoor allergens can cause asthma symptoms and attacks, as well as other allergic symptoms such as sneezing or a runny nose. It is therefore important to consider whether your asthma is caused or worsened by allergens.

Exposure to even small amounts of airborne allergens can cause asthma symptoms. Repeated exposure may not only provoke symptoms, but may also be a cause of long-term (chronic) inflammation in the airways.

Proper advice about which allergens and environments you should avoid can only be given after talking to your doctor and often after you have been tested for allergies.

Is asthma a psychological (psychosomatic) disease?

No, asthma is not a psychological condition, it is a long-term (chronic) inflammatory disease that leads to extra-sensitive and easily irritated airways, especially when it is not properly treated.

Although asthma is not a psychological condition, emotional stress can trigger the symptoms. For example, financial problems, not enjoying your work or worrying about your family can all help to trigger symptoms if you already have asthma.

Why is it sometimes so hard to know what triggers an asthma attack?

People with allergic asthma can often easily identify the most common trigger factor(s) for their asthma (e.g. pets or pollen). But many people with untreated or under-treated asthma have an underlying airway inflammation that they are hardly aware of. These people will react easily to many irritants, allergens and infections, and it can be difficult to identify the most important one.

If your asthma is provoked by more than one trigger at the same time, the reaction can be stronger than if you are only exposed to one trigger. For example, an airway infection may cause you to react to stimuli that you normally would not react to. This is why triggers such as physical exercise, strong smells, plants, chemicals, smoke, weather changes, anxiety, stress and some medications can sometimes cause an asthma attack and sometimes cause no symptoms.

Why does my asthma get worse when I am upset or worried about something?

Not all people with asthma feel worse when they are upset or worried. Those who do may be easily stressed, or may cry or breathe too fast (hyperventilate) easily.

Another reason that your asthma gets worse could be that you are not being treated properly for the inflammation you have in your airways.

Why do I not react when I meet my neighbour’s dog outdoors, although I react indoors?

A person with allergic asthma can be exposed to a certain amount of the allergen without reacting. In most cases, the concentration of allergens (except pollen) will be higher indoors than outdoors. You may also be exposed to higher levels of other allergens indoors, making the level of total allergens higher than what you can tolerate.

Can I really get asthma symptoms from a plastic Christmas tree?

Yes, you could if you had asthma symptoms from real Christmas trees in the past (though this is not a common allergy)! This phenomenon is called a ‘conditioned reflex’ – the same thing that causes your mouth to water when you see a picture of delicious food.