A fast acting solution that takes just 15 minutes to work. A thicker gel formulation which contains Penetrol® to aid the penetration of the louse egg. Fast acting to shorten treatment time. Clinically proven to kill head lice and eggs with just one application. Important Safety Advice - Hedrin Liquid Gel is slippery. Baths, shower cubicles etc. may become slippery when using or washing the hair. Take care. Wash any residues away with detergent and warm water.