Local sweating responses to conducting heat were tested in newborn infants during the first week after birth, under controlled thermal conditions. Two thirds of the mature, full-size neonates and a significantly lower proportion of premature low-brith-weight infants showed positive reactions. Minimal effective thermal stimulus exceeded thresholds defined for adults. Usually, full-size neonates with negative reactions to heating showed sweating responsiveness to local stimulation with epinephrine hydrochloride or acetylcholine chloride. The same dissociation of responses occurred in some low-birth-weight babies, while others were unresponsive to both kinds of stimuli.
These sweating deficits are of central nervous system origin, resulting from incompetence of autonomic centers. Functional immaturity of sweat glands cannot be ruled out as additional cause in neonates who failed to respond to either kind of local stimulation.