Can infections trigger asthma attacks? 

Respiratory infections, such as the common cold, influenza, and chest infections, are among the most frequent causes of asthma exacerbations in the United Kingdom. For individuals living with asthma, a viral or bacterial infection does not just cause typical cold symptoms; it directly impacts the hypersensitive lining of the airways. This interaction can lead to a significant increase in inflammation, making it much harder to breathe and potentially leading to a serious asthma attack. Understanding the relationship between infectious illnesses and lung stability is essential for effective self-management. This article provides a clear overview of why infections act as triggers, how to identify worsening symptoms, and the clinical steps you can take to protect your respiratory health during the cold and flu season. 

What We’ll Discuss in This Article 

• The biological link between viral infections and airway inflammation. 

• Why common colds often lead to a ‘secondary’ asthma response. 

• Identifying the difference between a standard cold and an asthma flare up. 

• Practical strategies to reduce the risk of infection related attacks. 

• The importance of the annual flu vaccination for asthma patients. 

• Clinical guidance on using your asthma action plan when you feel unwell. 

Do infections cause asthma symptoms to worsen 

Infections, particularly viral respiratory infections like the common cold or flu, are a primary trigger for asthma attacks. When a virus enters the respiratory system, it causes inflammation and swelling in the lining of the airways. For someone with asthma, whose airways are already prone to inflammation, this extra immune response can cause the bronchial tubes to narrow significantly. This narrowing restricts airflow, leading to common symptoms like wheezing, chest tightness, and a persistent cough. 

Medical data from the NHS suggests that a high percentage of asthma related hospital admissions are linked to viral infections. These illnesses can make the lungs more sensitive to other triggers, such as cold air or pollution, creating a compounding effect. Even a mild ‘sniffle’ can cause a significant drop in peak flow readings for some patients, highlighting the need for vigilance whenever an infection is suspected. 

• Viral infections are the most common cause of asthma flare ups in children and adults. 

• Symptoms of an infection related attack may persist long after the initial cold has cleared. 

• Proper use of preventer inhalers is the best way to reduce the impact of an infection. 

How infections impact your lungs 

When you catch a cold or the flu, the virus attacks the cells lining your respiratory tract. This causes your immune system to send white blood cells to the area, resulting in swelling and the production of excess mucus to ‘trap’ the virus. In a healthy person, this leads to a stuffy nose or a mild cough. However, in a person with asthma, this inflammation spreads deep into the smaller airways, causing them to twitch and tighten. 

The excess mucus produced during an infection can also block the already narrowed airways, making it even more difficult to move air in and out. This process is why people with asthma often feel much more breathless than those without the condition when they have the same viral illness. The recovery period for the lungs is also typically longer, as the internal inflammation can take weeks to fully subside after the virus has been defeated. 

• Airway Swelling: The immune response causes the bronchial walls to thicken. 

• Mucus Overproduction: Sticky phlegm further obstructs the narrow passages. 

• Increased Sensitivity: The ‘twitchy’ airways react more violently to everyday irritants. 

Causes of infection related asthma flare ups 

The primary cause of these flare ups is the direct invasion of respiratory viruses, such as rhinovirus (the common cold), respiratory syncytial virus (RSV), and the influenza virus. These pathogens are highly contagious and spread through respiratory droplets in the air or on surfaces. While the virus itself is the initial trigger, the body’s own inflammatory response is what causes the asthma symptoms to escalate. 

Bacterial infections, such as pneumonia or acute bronchitis, can also trigger asthma, although they are less common than viral causes. These often require different treatments, such as antibiotics, but the impact on the asthma remains the same: increased airway resistance and reduced lung function. Environmental factors, such as being in crowded indoor spaces during winter, increase the likelihood of encountering these infectious causes. 

• Viral Pathogens: Rhinovirus and Influenza are leading culprits. 

• Bacterial Complications: Secondary chest infections can worsen baseline asthma. 

• Cross Contamination: Touching contaminated surfaces and then the face or mouth. 

Triggers and environmental factors 

During the cold and flu season, several environmental factors combine with infections to increase the risk for asthma patients. For example, the use of central heating indoors can dry out the air, which irritates the respiratory tract and makes it easier for viruses to take hold. Furthermore, damp and poorly ventilated homes can encourage the growth of mould, which is an additional trigger that can complicate a viral illness. 

Seasonal changes also play a role. The transition from autumn to winter often brings a ‘peak’ in asthma admissions because children returning to school share viruses in an environment where cold, damp air is also present. This ‘perfect storm’ of trigger infection, cold weather, and indoor allergens requires a robust management strategy, including the use of a personalised asthma action plan. 

• Dry Indoor Air: Can dehydrate the airway lining, making it more vulnerable. 

• School and Work Environments: High density areas facilitate the rapid spread of viruses. 

• Winter Weather: Cold air can aggravate the inflammation already caused by a cold. 

Differentiating between a cold and an asthma flare up 

It is important to recognise that a cold and an asthma flare up often happen simultaneously, but they are not the same thing. A cold usually begins with a sore throat, sneezing, or a runny nose. An asthma flare up is specifically related to the lungs and involves wheezing, a tight chest, or difficulty catching your breath. If your ‘cold’ symptoms include a whistling sound when you breathe or a cough that is worse at night, your asthma is likely being affected. 

Recognising this distinction helps you know when to use your reliever inhaler. While a reliever will not cure the underlying viral cold, it will help to open the narrowed airways caused by the asthma response. If you find that your cold is moving ‘to your chest’ and causing significant breathlessness, this is a sign that the infection has triggered a more serious asthma episode that needs immediate attention. 

Feature	Typical Viral Cold	Infection Triggered Asthma
Primary Location	Nose and throat	Chest and bronchial tubes
Sound	Sneezing / Sniffling	Wheezing / Whistling
Main Symptom	Runny nose / Sore throat	Chest tightness / Breathlessness
Relief	Rest / Fluids / Paracetamol	Reliever inhaler (blue)

Conclusion 

Infections such as colds and flu are powerful triggers for asthma attacks because they increase airway inflammation and mucus production. By staying up to date with vaccinations, practising good hygiene, and following your personalised asthma action plan, you can significantly reduce the risk of a serious flare up during an illness. Always ensure you are using your preventer inhaler correctly to keep your lungs as resilient as possible against seasonal viruses. 

If you experience severe, sudden, or worsening symptoms, call 999 immediately. 

Authority Snapshot 

This article was written by Dr. Rebecca Fernandez, a UK-trained physician with an MBBS and extensive experience in cardiology, internal medicine, and emergency care. Dr. Fernandez has managed critically ill patients in intensive care units and has a deep understanding of respiratory physiology and infection management. Her expertise ensures that the information provided is clinically accurate, safe, and aligned with NHS and NICE standards for asthma care in the UK.