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.
Several common problems can cause air conditioner freeze-ups: 1  Insufficient Air Flow: Anything that restricts air flow will cause the temperature of the systemâs evaporator coil to drop below freezing. Humidity in the air will collect on the coil causing ice to build-up and diminish the systemâs cooling capacity.