PQ7 is basically a harmless and beneficial substance. It is usually found in modern shampoo products, to prevent the static charging of the hair, thus making it easier to comb.
Basically, it acts as a quasi “lightning rod” for the hair. Due to their own static charge these molecules get temporarily attracted to the hair, and “stick out” like real lightning rods on the rooftops. This protruding end of the molecules will connect to water molecules, and thus the PQ7 molecule acts as a channel to transfer the hair’s static charge to the water molecule. However, this connection is strictly physical in nature.
The static charge of the hair is absolutely natural and unavoidable: our clothes contain plastic fibres, our shoes usually have rubber soles acting as insulators, we are exposed to electrosmog – just to name a few sources of static electricity. Beyond making the hair easier to comb, eliminating the static charge of the hair also contributes to decreasing the occurrence of those annoying electrostatic fields around us.
Click this link for more information regarding the mechanism and environmental compatibility of PQ7: the environmental compatibility of PQ7.