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;.
Water leaks in central air conditioners are almost always caused by a problem with the condensate pan or drain pipes. The most common of those problems is a clogged drain line. When your condensate drain line gets clogged, water backs up and builds up in your pan. With nowhere to go, that water will begin to leak over your drain pan and onto your system and your floor. Another problem that can lead to a water leak is a crack somewhere in the pan or in the drain pipes.
Either way, this causes your evaporator coil to drop below freezing and your air conditioner to freeze up. Here are some common causes: 1  Insufficient air flow across your air conditionerâs evaporator coil can cause it to freeze up., you can figure out why your central air conditioner is icing up. Your air conditioner can freeze up for a variety of reasons, so we will discuss them from the most common to some of the more rare causes of ice up.