Antihistamines, H1. Histamine antagonists or antihistamines are drugs that relieve allergy symptoms.Histamine is a chemical used to identify and remove substances that trigger an allergic response. Ã¢ There are four histamine receptors &#40;designated H<sub>1</sub>, H<sub>2</sub>, H<sub>3</sub>, H<sub>4</sub>&#41;.
Quick Answer. Blocked condensation drain lines often cause excessive amounts of water in an air conditioner drain pan. These lines are designed to funnel excess water from condensation away from the air conditioning system inside the home. If these lines become blocked, the excess water drains into a drain pan.
1 Mechanical failures can cause your air conditioner to freeze up. 2  If there is a kink in your refrigerant lines, a blower fan that is not running or is dinged and out of balance, or a clogged filter dryer, then this too will change the pressures in your system and can make your central air conditioner freeze up.