New Insights into Neonatal Hypersensitivity

Abstract

The skin, the largest sensory epithelium of the body, plays a pivotal role in the homeostasis of organisms and is densely innervated by a wide variety of sensory neurons that have evolved to safeguard its integrity. Nowhere is this more important than in newborns, whose immune systems are not yet fully mature and for whom skin damage can therefore have serious immediate and long-term impacts on the viability of the organism as well as overall function of the skin sensory system. Attesting to this early vulnerability, newborn mammals of all species, including man, display a pronounced hypersensitivity to tactile stimuli over a protracted post-natal period (reviewed in [1]). Throughout this period of cutaneous hypersensitivity, protective withdrawal reflexes exhibit inordinately low activation thresholds and thus can be triggered by relatively innocuous stimuli. Rather than representing a paradoxical, maladaptive behavioural response, this hypersensitivity is undoubtedly highly adaptive in view of the pivotal importance yet extreme vulnerability of the integument and its associated protective/immune functions during early ontogeny.