Platelets, also called thrombocytes (thromb- + -cyte, blood clot cell), are a component of blood whose function (along with the coagulation factors) is to stop bleeding by clumping and clotting blood vessel injuries.
Milk of the poppy is essentially the Westeros version of morphine. Maesters make it from crushed poppy flowers, and morphine and other opiate-based drugs are made from poppy plants. Indeed, the books' descriptions strongly suggest that the poppy is intended to be the real-world opium poppy (Papaver somniferum).
There is no pus in milk. One of the biggest misconceptions I read about milk online today is that milk has pus in it. Itâs a common myth that is nearly always pushed by people who want you to stop drinking milk. Itâs used to scare people, and play on their emotional fears to get them to stop drinking milk.