Suffixes -algesia/-esthesia refer to lack of sensitivity to pain (-algesia) or abnormal sensitivity to stimuli (-esthesia). There are several types of analgesia including epidural analgesia which involves injecting anesthetic into the spine to relieve pain during childbirth, infiltration analgesia which uses subcutaneous injections to paralyze nerve endings at the operation site, and relative analgesia which uses nitrous oxide to elevate the pain threshold during dental procedures without full anesthesia. Hyperesthesia is an abnormal increase in sensitivity and can occur in the skin, ears, muscles, eyes, or sense of touch.