Some common kinds you can buy over the counter include: Note: Some antihistamines are mixed with other medicines.
When you get injured or your immune system detects a potentially dangerous foreign substance, certain white blood cells and tissue cells release histamines that seek out and attach to other cells that have a histamine receptor.Antihistamines are often combined with decongestants and/or pain relievers.If you take a combination medicine, it’s important to know each active ingredient.Here, the histamines induce an inflammatory response — they dilate the blood vessels, increasing blood flow to the site of injury or invasion.They also make blood vessels more permeable, allowing proteins and white blood cells to seep into the damaged or infected tissue.Many of the brand names above are for these combination medicines.These are meant to treat many symptoms at the same time.First-generation antihistamines may make you feel sleepy.This can affect your ability to drive or operate machines. Alcohol can increase the drowsiness caused by antihistamines.These were some of the first antihistamines scientists developed. They also work in the part of the brain that controls nausea and vomiting. One of the most common side effects of first-generation antihistamines is feeling sleepy.For this reason, they are sometimes used to help people who have trouble sleeping (insomnia).