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.
Quick Answer. Flooded or fluid-filled lungs, or pulmonary edema, occurs when air sacs in the lungs fill with fluid, according to the Mayo Clinic. Causes of pulmonary edema include a weakened left ventricle in the heart, trauma, drowning, high altitude and reactions to drugs or toxins.