Eli5: what is happening internally when a pimple forms and then it slowly turns into a zit with a white top that can ooze the white stuff (pus?) ?



Pretty much what the title says:
The zit starts off as a normal pimple, often times painful before it even begins to show and then after a few days has that dry, white appearance. Where is the pus all these days before and what causes it to turn into the zit?

In: Biology

It basically boils down to a small-scale bacterial infection. To get rid of it, the body causes a local inflammation, guiding more blood to the infected area and making it swell. In said blood are white blood cells, which start killing off whatever bacteria they can find. Dead bacteria and white blood cells finally form the “pus”, which gets its usually yellow-whitish color from them. As the clogged-up pore forming the original pimple still is there, said pus can not flow out and forms the classical white-head.

Most zits are caused by clogged pores. Oils, dirt, and even just some surface bacteria can get into a pore and cause it to clog. This triggers an immune response.
At first it’s just inflammation and usually an oil plug or “black head” which causes that swollen, painful, but not yet zit experience. When the body fails to expel that long enough, it starts sending in white blood cells, both to defeat bacteria and to try and break down that clog. This is where you get pus, an army of white blood cells keeping the budding infection from spreading.

This is also why zits are commonly lanced and you don’t want to squeeze them. They can burst inward, shooting 8nfectious material and pus deeper into your body causing infection to spread.

It can seem very sudden, but it’s a somewhat gradual process that… Well… comes to a head once enough pressure builds up and the infection has inflated the pore to near failure. The head is either the plug or a weak spot in your skin near the pore showing the pus through.