What are some common allergens that affect the respiratory system?

Pollen and mold are well-known common allergens that significantly impact the respiratory system. Pollen, which is often released by trees, grasses, and weeds during certain seasons, can trigger allergic reactions in susceptible individuals, leading to symptoms such as sneezing, nasal congestion, and even asthma attacks. Mold spores, found in damp environments both indoors and outdoors, can provoke similar respiratory issues when inhaled.

The other choices, while they may relate to respiratory conditions, do not constitute typical allergens in the same way. High humidity can exacerbate conditions but is not an allergen itself. Cold air may trigger symptoms in those with asthma or bronchial hyperreactivity, and exercise can lead to exercise-induced bronchoconstriction, but these are also not allergens. Lastly, while pet dander can cause allergies, medications are not classified as allergens. Hence, the identification of pollen and mold as common allergens accurately reflects their role in affecting respiratory health.