Psoriderm scalp lotion contains two active ingredients distilled coal tar and lecithin coal tar has been used in skin conditions for hundreds of years but it is still not fully understood how it works mainly because it is made up of so many different compounds it has mild antiseptic and anti inflammatory effects and relieves itching it is also absorbed into the skin cells and is thought to inhibit dna replication in these cells this slows down cell division and stops the cells from multi