Similar to other organophosphate insecticides, parathion acts by inhibiting cholinesterase, an enzyme essential for the proper functioning of the nervous system. Through this action, the substance is able to effectively kill a wide range of insects and mites. Unfortunately, however, parathion may also affect the human nervous system and is highly toxic no matter how it enters the body. Indeed, there have been documented fatalities of individuals exposed via ingestion, absorption through the skin, and inhalation. When acute poisoning occurs to a lesser extent, a number of symptoms may occur, including nausea, vomiting, pallor, stomach cramps, sweating, tearing of the eyes, vertigo, and confusion. Severe poisoning may be accompanied by slurred speech, loss of coordination, tremors, weakness, and paralysis.