Humid conditions and asthma flare-ups – understanding the connection

Asthma is a chronic inflammatory lung disease characterized by episodes of breathlessness, wheezing, and cough due to complex genetic–environmental interactions leading to airway inflammation and remodelling. Over the past few decades, various researches have shown a link between exposure to extreme weather events and asthma morbidity and mortality.

Various epidemiological evidence indicates that heat waves, cold spells, dust storms, hurricanes, floods and storm surges often cause worsening of underlying asthma, shedding light on the role of environmental factors, particularly the extreme weather conditions, in predicting asthma morbidity and mortality.

Hot and humid weather can directly or indirectly affect patients with asthma. Humidity basically refers to the moisture or water vapour content in the air. Ideally humidity of 25-35% is conducive.

How does increased temperature and humidity affects asthma patients?

Hot weather can cause dehydration that precipitates electrolyte imbalance and lactic acidosis, resulting in an asthma attack.
• A hot and humid weather also causes irritation of bronchial tubes, resulting in bronchoconstriction.
• Humid weather causes dense accumulation of air pollutants and sulphur dioxide that can worsen asthma symptoms.
• Humidity in the air also favours mould growth and pollen.
• Higher humidity and temperature causes elevation of ground level ozone, a layer formed due to excessive emission of pollutants emitted by vehicles, industries, and power plants. Ozone (smog) aggressively irritates lung tissue by reacting chemically with it, triggers both respiratory and cardiovascular system. Immediate problems include shortness of breath, coughing, asthma flare-ups, and increased risk of lung infections and inflammation. High levels of ozone or long-term exposure can worsen the symptoms, especially for those with asthma or other chronic lung diseases which may require emergency attention. However, stroke, heart attacks, and premature death are rare.

Common symptoms associated with excessive heat and humidity:

• Worsening of asthma episodes that present with cough, chest tightness, wheezing, worsening of breathlessness and may worsen underlying allergic rhinitis.
• Cause heat stroke and dehydration that may present with fatigue, reduced urine output, cold and clammy skin, palpitations, dark urine colour.
• There have been studies which have documented that after experiencing hot, humid air (49°C and 75–80% humidity) for 4 minutes, people with asthma had a 112% increase in airway resistance as opposed to the healthy group that only had a 22% increase in airway resistance.

How to manage symptoms and asthma flare-ups?

• Early identification of symptoms: cough, breathlessness, wheezing. Immediate addressing of the symptoms with inhalers for symptomatic relief.
• Monitoring of air quality index: Staying indoors when temperature and humidity is high.
• Using air conditioning and dehumidifiers inside.
• Using air filters with HEPA filter helps reducing the exposure to particulate matter.
• Using mask when going out.
• Adequate hydration.

In conclusion, hot and humid weather significantly worsens respiratory illness, especially chronic inflammatory lung diseases such as asthma. Hence it is crucial for individuals with asthma or other respiratory illness to be aware of environmental triggers and to take appropriate measures to minimize the exposure. By staying informed and prepared asthmatics can manage their symptoms and maintain their quality of life even in hot and humid conditions.

This article is authored by Dr. Suhas H S, Consultant – Pulmonologist, Manipal Hospital, Sarjapur Road