antihistamine. a drug that counteracts the effects of histamine, a normal body chemical that among its actions is believed to cause the symptoms of persons who are hypersensitive to various allergens.hile the term antihistamine can broadly include any agent that blocks any histamine receptor, in practice it is usually used to denote those blocking the H 1 type of receptors (H1 receptor antagonists), those involved in allergic reactions.
The Executive Branch. From the President, to the Vice President, to the Cabinet, learn more about the Executive Branch of the government of the United States. The power of the Executive Branch is vested in the President of the United States, who also acts as head of state and Commander-in-Chief of the armed forces. The President is responsible for implementing and enforcing the laws written by Congress and, to that end, appoints the heads of the federal agencies, including the Cabinet.
Branches of Government. Learn about the executive, legislative, and judicial branches of the U.S. government. About the Organization of the U.S. Government. The U.S. federal government is divided into three branches: the executive, the judicial, and the legislative. Executive Branch. The executive branch carries out and enforces laws. It includes the President, executive departments, independent agencies, and other boards, commissions, and committees. Judicial Branch