Cerebral lateralization and histamine skin test asymmetries in humans

Although asymmetries exist in both cerebral and somatic systems, their relationship is not well understood. One hypothesis suggests that some processes determining cerebral hemispheric dominance also affect immune systems. We employed histamine, a final common mediator for the immediate hypersensitivity immune response, to examine the relationship of skin response to cerebral lateralization (ie, left versus right brain dominance). Histamine skin wheal responses on the left and right forearms were measured using computerized planimetry in 176 consecutive patients undergoing allergy skin testing. Cerebral lateralization was determined by personal and family handedness via questionnaires. Subjects were classified as right handed (RH) with only RH relatives, RH with non-RH relatives, or non-RH (ie, left-handed or ambidextrous). Left/right arm asymmetries in wheal area were demonstrated and were related to cerebral dominance, but could not be explained by simple arm use. Right-handed subjects with only RH relatives had greater wheal size on the right arm, RH subjects with non-RH relatives had no significant left/right difference in wheal size, and non-RH subjects had greater wheal size on the left arm. Further, gender differences in these asymmetries appeared to be present for subjects with mixed cerebral dominance. The results suggest an association between processes affecting cerebral and somatic asymmetries, and offer new insight into brain/body interactions.