Final answer:
Antihistamines such as dextromethorphan and guaifenesin can work as cough suppressants.
Step-by-step explanation:
Antihistamines can work as cough suppressants by preventing mast cells from releasing histamines and causing allergic symptoms. By blocking the histamine H₁ receptors, antihistamines can alleviate symptoms such as itching, sneezing, and runny nose. Not all antihistamines are effective as cough suppressants, but examples of those that may have this property include dextromethorphan and guaifenesin. These substances can be found in some over-the-counter cough and cold medications.