Final answer:
Expectorants reduce the viscosity of secretions, allowing for more productive coughing. They are designed to help clear mucus and phlegm from the respiratory tract, not to treat allergic rhinitis symptoms like a runny nose and watery eyes.
Step-by-step explanation:
Expectorants are substances claimed to make coughing easier by reducing the viscosity of secretions, enhancing the production of mucus and phlegm. Unlike substances that suppress coughing itself, which work on the nervous system to suppress the cough reflex, expectorants help you cough more effectively when dealing with a "productive" cough, meaning a cough that brings up mucus. Therefore, the effect of expectorants is B- Reduction of the viscosity of secretions.
For allergic rhinitis, treatments may provide relief by producing mild sedation and reducing symptoms such as a runny nose and watery eyes. It should be noted that treating allergic rhinitis is not the primary function of expectorants. Instead, treatments like antihistamines or nasal decongestants like pseudoephedrine are more effective for these symptoms.