What can contribute to lower humidity levels, potentially exacerbating upper respiratory infections?

• A. Rainy weather
• B. Indoor heating systems
• C. High outdoor temperatures
• D. Increased air circulation

Answer: (B)

Dry air in the nose and throat makes it harder for the upper respiratory tract to defend itself. When humidity is low, the mucous membranes become dry and the mucus layer can thin, which slows the cilia-driven clearance of pathogens and irritants. That weakened barrier can worsen symptoms and may make infections more likely to take hold.

Indoor heating systems are a primary way indoor air becomes dry. Heating air increases its capacity to hold moisture, so unless extra moisture is added, the relative humidity drops. The resulting dry indoor air irritates the nasal passages and throat, dries mucus, and can amplify URI symptoms.

Rainy weather tends to raise humidity, not lower it; high outdoor temperatures don’t inherently cause lower indoor humidity, and increased air circulation can either dry or humidify air depending on the environment, but its effect on humidity is less direct than that of heating.