Final answer:
Decongestants are substances typically used to relieve excessive mucus in nasal pathways, facilitating easier breathing by reducing swelling in the nasal passages.
Step-by-step explanation:
Substances typically used to relieve excessive mucus in nasal pathways are decongestants. Decongestants like phenylephrine and pseudoephedrine act as sympathomimetic drugs, which means they stimulate adrenergic receptors and help to reduce swelling in the nasal passages, allowing for easier breathing. These are not to be confused with expectorants, which are substances claimed to make coughing easier while enhancing the production of mucus and phlegm, or with cough suppressants, which suppress the coughing reflex itself. For conditions like allergic rhinitis, decongestants may also help in reducing symptoms such as a runny nose and watery eyes. However, it is important to note that antibiotics are not effective for colds or the flu, as these are viral infections and antibiotics work against bacteria.