Antihistamine Antihistamine is a medicine that is used to counteract histamine, the chemical released from certain cells during an allergic reaction. Antihistamines suppress the symptoms associated with histamine, but they do not alter the original cause of the reaction. They are used especially in the treatment of hay fever and certain other allergies. Antihistamines should be used with caution. Many cause drowsiness, and users are warned to avoid taking them before driving an automobile, operating dangerous machinery, or drinking alcohol.
Some tolerance usually develops over a week or two to the sedative action of antihistamines.
Antihistamines often cause dry mouth, may cause a fast heart rate, or may, unless taken with food, irritate the stomach. Although antihistamines do not cure the common cold, they may be effective in alleviating some of the symptoms of the disorder. Inc. All Rights Reserved. From The World Book Rush-Presbyterian St. Luke's Medical Center Medical Encyclopedia . Inc. Email This to a Friend.