Cytokine expression correlates with differential sensory perception between lye and no-lye relaxers

Differences in perceived sensory scalp discomfort between guanidine carbonate/calcium hydroxide (no-lye) and sodium hydroxide (lye) relaxer technologies have been reported by users for decades. However, the biochemical processes responsible for the perceived differences have not been fully studied. We have used an in vitro three-dimensional skin model with well-developed epidermis to explore the expression of cytokines that may partially explain the biological response resulting in differences in sensory perception. The cytokines selected were prostaglandin E2 (PGE2), interleukin-1a (IL-1a), and IL-1 receptor antagonist (IL-1ra) because they have been shown to participate in irritant-induced discomfort. We show that lye relaxer induced over 350% increase in PGE2 expression over untreated control compared to 200% by no-lye in the early phase (4 h) postexposure epidermal response. Expression of IL-1a in the early phase showed no significant difference between lye and no-lye; however, no-lye induced higher levels (p < 0.0001) in 24 and 48 h. Concomitantly, no-lye induced increased expression of IL-1ra compared to lye at all time points. Given the association of PGE2 with nociceptive activation, these findings suggest that the perceived variation in sensory discomfort reported by consumers between lye and no-lye relaxers may be associated with differences in induced PGE2 expression.