How do antihistamines relieve cold symptoms?

Antihistamines are generally split into two categories: First-Generation OTC Antihistamines and Second-Generation OTC Antihistamines. First-Generation usually deals with cold and flu medications, while Second-Generation includes allergy medications. These are often combined with other drugs to control the symptoms of a cold caused by histamines. These medications compete with histamines by attaching to the histamine receptors in the body. This action stops histamines from attaching to cells and from making those cells leak fluid. In this way, antihistamines help to control congestion and drainage that are common in a cold and flu.