Trypanophobia is defined as the extreme fear of medical procedures involving injections or hypodermic needles. Although sometimes referred to as aichmophobia, belonephobia, or enetophobia, these terms may also refer to a more general fear of sharply pointed objects. In the medical literature, fear of needles is known as Needle Phobia. Since it is a phobia, it is defined as an irrational fear. It is estimated that at least 10% of American adults have a fear of needles, but it is likely that the actual number is larger as the most severe cases are never documented due to the tendency of the sufferer to avoid all medical treatment. Possible signs and symptoms of Needle Phobia when confronted with the sight of blood or a needle may include anxiety, increased heart rate, a drop in blood pressure, nausea, dizziness, and (more with Needle Phobia that almost any other) fainting.