Asthma is caused by inflammation of the airways, a long-term condition, which can cause
What is asthma?
cough, wheeze and breathlessness. The severity of the symptoms varies from
person to person, and can be well-controlled in most people, most of the time.
Cause of Asthma
In the UK, 5.4m people are currently receiving treatment for asthma, one in every 12 adults and 1 in every 11 children. Asthma in adults is more common in women than in men.
If you are diagnosed with asthma as a child, the symptoms of asthma may disappear during your teenage years. However, asthma can return in adulthood. If childhood symptoms of asthma are moderate to severe, it is more likely that the condition will persist or return later in life. However, asthma does not only start in the young, it can develop at any age.
The cause of asthma is not fully understood, but it is known that asthma often runs in families, and you are more likely to have asthma if one or both of your parents have the condition.
What is asthma?
Asthma is caused by inflammation of the airways – the small tubes that carry air in and out of the lungs (known as the bronchi). If you have asthma, this means the airways of the lungs (the bronchi) are inflamed and are more sensitive than normal. When you come into contact with something that irritates your lungs, known as ‘triggers’, your airways become narrow, the muscles around them tighten, and there is an increase in the production of sticky mucus, or phlegm. This makes it difficult to breathe and causes wheezing and coughing, and may make your chest feel tight.
A severe onset of symptoms is known as an asthma attack, or an 'acute asthma exacerbation'. Asthma attacks may require hospital treatment and can sometimes be life-threatening, although fortunately this is rare.
For some people with chronic (long-lasting) asthma, long term inflammation of the airways may lead to more permanent narrowing.
Triggers are anything that irritates the airways and bring on the symptoms of asthma. These differ from person to person and people with asthma may have several triggers.
Common triggers include house dust mites, animal fur, pollen, tobacco smoke, exercise, cold air and chest infections
Other types of asthma
There are also different types of asthma that can be made worse by certain activities:
- Work-aggravated asthma is a pre-existing asthma that is made worse by dust and fumes at work.
- Occupational asthma is caused by exposure to specific substances at work. For example, some nurses develop occupational asthma as a response to exposure to latex, and some workers in the food-processing industry develop occupational asthma as a response of exposure to flour.
The symptoms of asthma include:
- feeling breathless (you may gasp for breath),
- a tight chest (like a band tightening around your chest),
- wheezing (a whistling sound when you breathe, and
- coughing, particularly at night and early morning, and
- attacks triggered by exercise, exposure to allergens and other triggers.
You may have one or more of these symptoms. Symptoms that are worse during the night or with exercise can mean that asthma is getting worse and you should talk to your doctor or asthma nurse about this.
When asthma gets worse
When asthma symptoms get significantly worse, this is known as an asthma attack. A severe asthma attack usually develops slowly, taking between six and 48 hours to become serious. However, for some people asthma symptoms can get worse quickly.
As well as symptoms getting worse, you can tell that an asthma attack is developing when:
- you get more wheezy, tight or breathless,
- the reliever inhaler is not helping as much as usual,
- there is a drop in your peak expiratory flow (see the Diagnosis section for more information).
If you notice these things happening, do not ignore them. Instead, contact your GP or asthma clinic or consult your asthma action plan if you have one.
In a severe asthma attack, other things may happen:
- reliever inhaler (usually blue) does not help symptoms at all,
- the symptoms (wheezing, coughing, tight chest) will be severe and constant,
- too breathless to speak,
- a racing pulse,
- feeling agitated or restless,
- lips and/or finger nails may look blue.
Causes of asthma
There is no single known cause of asthma, but there are several factors that may contribute to the condition.
Contributory factors include a genetic predisposition (having something in your genes that makes it more likely that you will develop asthma), diet and the environment.
Known risk factors for the development of asthma include:
- a family history of asthma, or other related allergic conditions (known as atopic conditions), such as eczema, hayfever or allergic conjunctivitis (inflammation of the eyes),
- developing another atopic condition,
- having bronchiolitis as a child (bronchiolitis is a lung infection common among children),
- being exposed to tobacco smoke as a child, particularly if your mother smoked during pregnancy,
- being born prematurely, and
- being born with a low birth weight.
The symptoms of asthma can be triggered by a number of external factors as outlined below.
- Infections of the airways and chest (respiratory infections). These infections are mainly caused by viruses. Fungi, bacteria and parasites may also be responsible for causing respiratory infections in some people.
- Allergens, such as pollen, dust mites and animal fur or feathers can trigger asthma.
- Airborne irritants, such as cigarette smoke, chemical fumes and atmospheric pollution may also trigger asthma.
- Medicines, such as the class of painkillers known as nonsteroid anti-inflammatory drugs (NSAIDs), the most well-known of which are aspirin and ibuprofen, can in some cases trigger asthma. Also, a certain type of medicine, known as beta-blockers, which are used in the treatment of high blood pressure, can trigger symptoms of asthma.
- Emotional factors - asthma can be triggered by emotional factors, such as stress or laughing.
- Foods containing sulphites - sulphites are naturally occurring substances found in some food or drink. They are sometimes used as a food preservative. Food and drink high in sulphites include beer, wine, shrimp and many processed or 'pre-cooked' meals.
- Weather conditions, such as cold air, may trigger asthma.
What happens during an asthma attack
The symptoms of an asthma attack begin when something triggers a biological process called inflammation. Inflammation is one of the ways that our body's natural defence system, known as the immune system, helps fight off infection against viruses or bacteria.
If your body detects an infection in the lungs, it will start the process of inflammation. White blood cells will be sent to the site of the infection to destroy the infection and to prevent it spreading. White blood cells cause the airways to swell, and produce mucus.
If you have asthma, your airways are over-sensitive to the effects of inflammation. Too much mucus is produced and your airways swell more than they should. Also, as a response to the inflammation, the muscles surrounding your airways begin to contract, making the airways narrower and narrower.
It is the combination of mucus and the swelling and narrowing of the airways that makes breathing difficult and produces the wheezing and coughing that is associated with asthma. Left untreated, the cycle of symptoms can worsen, and your airways can become totally blocked, making breathing impossible. This is a very dangerous situation that can cause death.
If you or someone else is having a severe asthma attack, and you or they are unable to breathe, you should dial 999 immediately to request emergency medical treatment.
Diagnosing asthmaYour GP will normally be able to diagnose asthma by asking you about your symptoms, examining your chest and listening to your breathing.
They will want to know about your medical history and if you have a history of allergic conditions in your family.
Your GP will want to know about the circumstances surrounding the onset of your symptoms, such as when and where they occurred. They will also want to know if you have been taking any medicines, what your occupation is, and details about your work and home environment. This could help identify the possible trigger, or triggers, of your asthma.
People with asthma often lack signs of the condition, unless they are experiencing an asthma attack. This is because the degree of airway obstruction varies from person to person.
Signs that your GP will be looking for include wheezing when you breathe (although the absence of a wheeze does not rule out asthma) and an increased respiratory rate (the amount of times you breathe in and out during a minute).
Peak expiratory flow rate test
The diagnosis of asthma can typically be confirmed using a number of tests, the most popular being the peak expiratory flow rate (PEFR) test.
The PEFR test uses a small hand-held device known as a peak flow meter which can measure how much air you are able to breathe out of your lungs. A reading is taken, and you will then be given a medicine which is effective in treating asthma in the short-term. A second reading is then taken. If the reading is much higher after taking the anti-asthma medicine, then the diagnosis is normally confirmed.
You may be given a peak flow meter to take home with you, and a diary in which you can record measurements of your peak flow rate. This is a good way of recording how the symptoms of your asthma react to different circumstances.
If the symptoms of your asthma are different than normal (atypical) or you have additional symptoms, you may be referred for a chest X-ray. This is to rule out other lung conditions, such as chronic obstructive pulmonary disease (COPD) (a lung condition that is similar to asthma, but usually caused by smoking), bronchiectasis (inflammation of the airways of the lungs), or lung cancer.
Your GP should be able to identify exercise-induced asthma by asking you about your symptoms in relation to exercise. Common symptoms include a cough (which normally starts six to 10 minutes after exercise) and chest tightness (appearing up toone to twohours after exercise).
Your GP will also want to know about any symptoms not related to exercise, such as coughing at night or breathlessness. This can rule out the possibility that your exercise-induced asthma is being caused by poor asthma control.
Your GP might suspect that you have occupational asthma if you report that your symptoms are better on days you do not work, or when you are on leave. Occupational asthma may also be diagnosed if you work in an industry where there is a high risk of getting the condition. Example of high-risk occupations include:
- paint sprayers,
- bakers and pastry makers,
- chemical workers,
- animal handlers,
- food processing workers, and
- timber workers.
Your GP may ask you to take measurements of your peak expiratory flow rate both at work and when you are away from work, or on leave.
Your GP may then refer you to a specialist in occupational medicine, in order to confirm the diagnosis.
Tests can also be carried out to see if you are allergic or sensitive to certain substances that are known to cause occupational asthma.
Treatment of Asthma
While there is no cure for asthma, it can wax and wane across a lifetime. There are a number of treatments that can help to control the condition very effectively. Treatment is based on two important goals:
- Relief of symptoms.
- Preventing future symptoms and attacks from developing.
Successful prevention can be achieved through a combination of medicines, lifestyle advice and identifying and then avoiding potential asthma triggers.
Main asthma treatments
There are two main treatments for asthma - preventers and relievers. These come in a variety of delivery devices called inhalers, which enable you to breathe the medicine in through your mouth, directly into your lungs. The addition of a spacer device increases the medication delivered to the lungs.
Preventers are designed to quell swelling and inflammation in the airways and reduce mucus. This also reduces the sensitivity of the airways and so minimises potential damage.
The protective effect is built up gradually over a period of about a fortnight. Your medication must be taken daily to maintain protection, even if you are not experiencing symptoms.
Most preventers are based on corticosteroids, usually known as steroids. These are completely different from the anabolic steroids sometimes used by bodybuilders and athletes.
Most common types of preventer are inhaled steroids. These can include beclomethasone, budesonide, fluticasone. Occasionally, if your asthma is acute and severe, you may be given a short course of steroids taken as tablets, or even an injection. There are other non-steroid preventers, usually used for children, such as sodium cromoglycate and nedocromil sodium. They are usually taken three to four times a day and are not generally as effective as steroids.
Many people worry about the side-effects of steroids. High doses taken over a long period can have significant side-effects. For this reason, doctors will be careful to prescribe the lowest possible dose needed to control your asthma.
Potential side-effects of preventers
The main side effects are hoarseness and an increased risk of mouth and throat infections caused by thrush, a yeast that lives normally on the body's mucous membranes.
Using the inhaler before brushing your teeth and rinsing your mouth out afterwards helps to avoid this. Using a 'spacer' makes it easier to inhale the drug, and so helps reduce the risks of steroids being absorbed into your body.
Relievers are drugs that relax and open up the airways - medically known as bronchodilators - making it easier to breath. These are prescribed for the relief of asthma symptoms during an actual asthma attack, when peak flow readings are low and before exercise or activity to reduce the risk of an attack.
Because these drugs do not reduce swelling and inflammation of airways, you may also need to take a preventer.
Some relievers alleviate symptoms almost instantly (rescue relievers). Others have a longer lasting action (long-lasting relievers). The latter may be prescribed if wheezing, breathing difficulties and coughing persist despite using a preventer and a rescue reliever - or if symptoms come on in the night - nocturnal asthma.
Common rescue relievers are salbutamol and terbutaline. Another type of reliever (most often prescribed for babies under two and for older people) is called ipratropium bromide.
Long-acting relievers include oxitropium, salmeterol, and eformoterol, all of which are inhaled. Occasionally, theophylline-based drugs are taken by mouth, so tablets may be prescribed
Relievers, such as Ventolin, relax and open airways during an asthma attack.
Potential side-effects of relievers
Side effects are usually mild and pass away quickly. The main ones are a slightly increased heartbeat, and muscle trembling, especially in the hands. Some oral relievers may cause dry mouth, blurred vision, difficulties passing urine, or constipation. Theophylline-based drugs, which relax the muscles in the walls of the airways, can occasionally cause nausea, more rapid heart rate, a nettle-like rash, dizziness, nervousness, headaches, irritability or restlessness.
Always report any unusual symptoms to your doctor.
Complications of asthma
Quality of life
Badly controlled asthma can have an adverse impact on your quality of life. The condition can result in:
- underperformance or absence from work (in the UK, asthma accounts for at least 12.7 million work days lost each year), and
- psychological problems including stress, anxiety and depression.
If you feel that your asthma is seriously affecting your quality of life, you should contact your GP or asthma clinic. Your personal asthma treatment plan may need to be reviewed in order to better control the condition.
Asthma charities and support groups will also be able to provide help and advice.
Asthma can lead to a number of possible serious respiratory complications, including:
- pneumonia (infection of the lungs),
- a collapse of part or all of the lung,
- respiratory failure (a condition where the levels of oxygen in the blood become dangerously low, or the levels of carbon dioxide become dangerously high), and
- status asthmaticus (severe asthma attacks that do not respond to treatment).
All of these complications are life-threatening and will need medical treatment.
In the UK in 2005, over 1300 people died from asthma, and on average one person dies from asthma every seven hours. The risk of dying from asthma increases with age.
In England between 1996 and 2004, there were 16,384 asthma-related deaths in people aged over 65, compared with 239 deaths in children under 15 years of age. Deaths are more common in women than in men, but this could be due to the fact that women tend to live longer.
However, a leading asthma charity has claimed that 90% of these deaths could have been prevented through proper management of the condition.
If you are a smoker and you have asthma, you should stop smoking. This will significantly reduce the severity and the frequency of your symptoms. Smoking can also reduce the effectiveness of asthma medication.
The NHS Smoking Helpline can offer you advice or encouragement. You can call on 0800 022 4 332, or visit the NHS Smokefree website.
Your GP or pharmacist will also be able to provide you with help and advice.
If you do not smoke and you have asthma, you should still avoid exposure to tobacco smoke.
Due to the increased risk of complications, people with severe asthma are recommended to receive vaccinations for influenza (flu) and pneumococcal (a bacterium that can cause pneumonia, meningitis and infection of the blood).
It is important that you identify triggers where possible, by making a note of any worsening symptoms or by using your peak flow meter during exposure to certain situations. Some triggers, such as air pollution, viral illness or certain weather conditions, can be hard to avoid. However, it may be possible to avoid other triggers, such as dust mites, fungal spores or pet fur.
Weight, diet, and exercise
Maintaining a healthy weight will help you to control your asthma more effectively. The key to maintaining a healthy weight is having a healthy diet and taking regular exercise.
A low fat, high fibre diet is recommended, including plenty of fresh fruit and vegetables (five portions a day) and whole grains. Thirty minutes of moderate exercise a day, at least five times a week, is also recommended. The exercise should be vigorous enough that it leaves your heart beating faster and you should feel slightly out of breath. Examples of moderate exercise are going for a brisk walk, or walking up a hill.
If your asthma is well managed, moderate exercise should not normally cause any problems. However, see your GP if you experience symptoms of asthma during or after exercise.
As well as the factors outlined in the causes section, there are a number of other medical conditions, such as rhinitis and sinusitis, that are known to aggravate the condition. Therefore, if you get the associated symptoms of these conditions, you should report them to your GP. Treating these conditions will not necessarily make your asthma better, but it should stop it getting out of control. These conditions are listed in more detail below.
Rhinitis is an inflammation of the lining of the nose. It can be caused by an infection, such as the common cold, or can be a response to an allergen, such as pollen. The symptoms are sneezing, a blocked, stuffy or runny nose, and an itchy nose, throat and eyes.
Sinusitis is an inflammation of the small air-filled cavities inside the cheekbones and forehead. It is caused by infection. The most common symptoms are a throbbing pain that is worse when you move your head, a blocked or runny nose, and a high temperature.
Gastroesophageal reflux disease
Gastroesophageal reflux disease is a condition of the digestive system where acid leaks back from your stomach into your oesophagus (gullet). The main symptoms are heartburn (a burning pain behind your breastbone), stomach pains, and bloating and belching.
Sleep apnoea is a sleep disorder where the upper airway in your throat collapses repeatedly, at irregular intervals, during sleep. You may be affected by sleep apnoea but remain unaware that you have the condition.
However, as your sleep is disrupted you should begin to experience symptoms during the day, and your partner may witness an episode of sleep apnoea, or point out other symptoms that occur at night. Symptoms include snoring, lack of concentration during the day time, and frequent awakenings during the night.
- Allergy UK - A national medical charity set up to increase understanding and awareness of allergy, to help people manage their allergies, and to provide training in allergy for health care professionals. You will find information, advice and support on all the common allergies, and obtain details of your nearest NHS allergy clinic and the allergy specialist involved.
- Asthma UK - This tells you about asthma, treatments, news, education, research and support. There are leaflets for people with newly diagnosed asthma, a movie What's asthma all about? and details of an Asthma Helpline run by trained nurses. The Helpline number is 08457 010203.