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Home / Asthma / Unmasking asthma triggers: what causes flare-ups

Unmasking asthma triggers: what causes flare-ups

Learn more about what triggers asthma symptoms

Asthma is a common condition that affects your lungs and causes breathing difficulties. This makes your airways more sensitive to things healthy lungs would not react to, such as pollen or car fumes.

Young woman using inhaler suffering from asthma attack.

These factors can trigger or worsen symptoms, which puts you at an increased risk of an asthma attack.

Not everyone’s triggers are the same. But, over time and once you learn more about your symptoms, you can effectively manage your condition. Keep reading to find out the various asthma triggers and how to avoid them.

What are asthma triggers?

Asthma triggers are things in the environment or your lifestyle that can make your symptoms worse. With asthma, your lungs are sensitive to certain triggers.

When you come into contact with a trigger, the airways narrow. The lining of your airways becomes swollen and inflamed. It can also cause mucus to build up in your airways. This can cause your symptoms to worsen and could result in an asthma attack.

A variety of things can be triggers. It could be things in the environment like pet dander or pollen. It can also be lifestyle factors, such as your diet or stress. We will discuss all the different factors and how they affect your airways.

Indoor and outdoor asthma triggers

Some of the most common triggers are in your home or outside. They are natural elements that affect your airways in a plethora of ways. Most people will be affected differently depending on the time of year or the environment that they’re in.


Allergic asthma is a type caused by the same elements that cause hay fever:

  • pollen
  • pet dander
  • dust mites
  • mould

These substances, when you breathe them in, can irritate your airways and cause symptoms. For some people, hay fever symptoms occur alongside asthma flare-ups.


Air pollution is anything that makes the air more toxic. It is more common in cities. Some sources of air pollution include:

  • busy roads
  • quarries
  • industrial sites
  • building sites
  • anywhere fossil fuels are burnt (e.g. coal and oil)
  • wood burning
  • natural sources (e.g. volcanoes, sea spray and pollen)
  • fireworks or bonfires

It affects your health in many ways, but it is especially bad for your lungs. It irritates the airways and can deep into the lungs, causing inflammation.

Photo of pollution coming from car exhausts.

Early exposure can increase a child’s risk of developing asthma because their lungs are still growing. It can also put an unborn baby at risk if you’re pregnant.


Weather changes affect our bodies in numerous ways. This is no less true for people with breathing problems.

Winter Winter

The cold, dry air can irritate your airways. It can also promote mucus production, as cold air makes you more congested. You are also more likely to get a cold or flu during the winter.

Summer Summer

Some people find it more difficult to breathe when the air is more humid. Additionally, there are more pollutants and pollen in the air.

Thunderstorms Thunderstorms

The humid air can make it more difficult to breathe. During the summer, windy weather can spread more pollen and allergens.

Rain Rain

Rain can make a pollen reaction worse. Rain droplets can split pollen into smaller particles. This means pollen can get deeper into your lungs and cause a worse reaction.

Asthma and lifestyle

Certain lifestyle habits may make your asthma worse.


When you inhale tobacco smoke, either from smoking yourself or secondhand smoke, it irritates the airways, causes inflammation and promotes mucus production. It can also make you more resistant to asthma inhalers.

Close-up of a hand holding a burning cigarette.

Smoking causes a lot of health problems, not just asthma. Your doctor or asthma specialist will advise you to quit smoking.

Want to quit smoking?

Learn more here


Certain jobs put you more at risk of flare-ups or childhood asthma returning as an adult. This is known as occupational asthma.

It is common in jobs that involve certain allergens or irritants, such as:

  • floor dust and additives
  • latex (e.g. latex gloves in healthcare settings)
  • animal fur, skin and saliva, as well as dust from enclosures
  • grain and poultry dust
  • vapours and particles from surgical techniques in hospitals
  • chemicals in car spray paints
  • the bleach used in hair salons
  • wood dust from machining or sanding
  • fumes, mists and vapours from electronic, engineering or metalwork
  • chlorine in indoor pools

People with occupational asthma may be worried about changing or losing their jobs. However, talk to your employer and/or your healthcare provider to see if they can find a solution.


Asthma can get worse whilst exercising.

When you exercise, you breathe more through your mouth. This makes you breathe air that’s colder and drier than when you breathe in through your nose. This can trigger symptoms.

Young woman out of breath from exercising.

This is different from exercise-induced asthma. This is a condition that causes asthma-like symptoms after exercise in people who don’t have asthma.

Exercise is still important to help manage your asthma. Keep your reliever inhaler handy whenever you do exercise. Your doctor will help form a plan with you for when you do physical activity.


Recreational drugs cause side effects that may trigger your asthma, such as:

  • shallow breathing
  • intense emotions - which may affect your breathing
  • increased risk of chest infections
  • lung damage
  • nasal irritation
  • feeling energised - which may cause you to do more physical activity

If you use drugs regularly, it’s also more likely you’ll forget to use your asthma medications regularly.

Other asthma triggers

Cold & flu

Cold and flu are two of the most common asthma triggers. They can also make asthma attacks more serious if your asthma is not managed. When you have a cold or flu, your airways become inflamed and you produce more mucus.

Hormonal changes

A more surprising trigger is hormones.

Some women report their symptoms get worse during their period, pregnancy or perimenopause.

Experts aren’t sure why this happens. They believe it’s because hormone fluctuations increase inflammation across the body, which increases inflammation in the airways.


Stress has a huge impact on the body, whether short-term or long-term. It can also make your symptoms worse in several key ways:

  • it affects your immune system, which means you’re more likely to react to triggers than when you’re not stressed
  • emotions like anger can cause symptoms
  • you may engage in habits that can affect your breathing like smoking or drinking
  • you may forget to take your medicine regularly

You should assess what’s causing stress in your life as it will help your asthma. If you have chronic stress, you may need therapy. Ask your GP for treatment solutions.


You may trigger asthma symptoms if you eat a food you’re sensitive to or allergic to. Common food allergens include shellfish, eggs, milk, tree nuts, peanuts and soya.

Additionally, certain foods release chemicals that trigger symptoms. Wine, yogurt, mature cheese and smoked meats can release histamine - a chemical that is released during an allergic reaction.

Processed meats, pickled foods and dry fruits contain certain preservatives that may cause some people to have flare-ups.

How do I manage my asthma triggers?

How you manage your asthma will depend on your triggers. For example, if pollen is a trigger for you, take antihistamines before you leave the house.

Discuss your triggers with your GP or asthma nurse. They can help with you how to avoid them. Add them to your asthma action plan to remind yourself and those around you.

Close up of young woman reaching for her asthma inhaler.

You should also use your asthma medicines correctly. Take your preventer daily and exactly as prescribed by your doctor. This alone will decrease the risk of reacting to your triggers significantly, prevent asthma attacks and control symptoms.

Learn more about asthma

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Learn more about asthma treatment and management at euroClinix by checking out our other information pages.

Medically reviewed by Dr. Caroline Fontana Written by our editorial team Last reviewed 20-12-2023

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