What just spattered over my monitor? (Probaby TMI)

Factual Questions
1

So, I rolled up my sleeves, about to do some serious coding work, and I noticed a red mark on my forearm.

“Hmm,” I thought to myself. “Haven’t seen that before. Insect bite? Incipient spot?” So, I gently pinched the skin between my finger and thumb, meaning only to inspect it …

SPLIP!!

Ah. Not an incipient spot at all then.

So, as I was wiping my monitor afterwards, it occurred to me to wonder exactly what it was I was wiping off. And it occurred to me that I know exactly where to ask this question, don’t I?

A search for “squeezing zits”, as you might imagine, yielded a great deal of material. (I would have searched for “pus”, but it’s only three letters). However, the stuff I turned up, entertaining though it was, didn’t really answer my question. Lots of descriptive stuff - “waxy white ooze”, “looked like green playdough”, “malleable lump of goo” - all very well, but what I want to know is the composition, dammit, not the mere outward appearance. The best I could get was “white blood cells, cellular debris, and necrotic tissue”, which seems vaguer than I would like.

And how come it builds up so much pressure? My arm was more than a foot from my monitor … now, I can propel a number of bodily secretions over much greater distances, but there’s usually muscular effort involved there … I mean, are we talking some kind of fermentation going on here?

I await your words of wisdom with a suitable feeling of agog-ness.

2

Partial answer: Certain invasive microbes are recognized by the immune system and the reaction is for white blood cells to approach and engulf the microbes and die. The white blood cells pile up and that is pus (and that is why pus is whitish). Being engulfed kills the microbes and stops them spreading.

In historic times, pus was called “healing pus”, as they recognized that it was a good thing. If the individual for some reason could not produce pus, certain infections would spread and finish off said invididual.

3

How is that vague? The skin pore gets blocked, trapping in sebum (skin oil) and bacteria. The bacteria begin feasting on the sebum. Yum! White blood cells to the rescue! White blood cells do their job and die honorably in the line of duty, forming puss.

It doesn’t. You applied the pressure yourself when you squeezed it, like popping the bubbles in bubble wrap. Fun! When the outer layer eventually ruptures from the pressure, you’ve got a tiny pinprick hole with the full force of your squeezing behind it.

4

But … forgive the graphicness … this was, well, a small but audible detonation, and a spray of over twelve inches, from what was meant only as a gentle exploration - certainly, I wasn’t exerting nearly the force I would need to pop bubble wrap. (Or course, I can’t state, in, umm, whatever the units would be - newtons? - how much force I was actually exerting at the time. But it really wasn’t very much at all.)

5

You don’t really need a lot of force. What you’re dealing with is a system that acts a little like a hydraulic jack. You apply gentle pressure to the area in question, and that pressure is transferred to the pimple. If the pressure is enough (and it doesn’t have to be much) to rupture the surface, you end up will basically all the pressure you are applying focused on a single point.

As an example, consider a hypodermic syringe. All you have to do is barely depress the plunger, and the contents will squirt a considerable distance. The narrower the needle, the farther it squirts.

The same physics apply here. Pressure = Force * Area. You start out by applying a small force to a large area, and end up having that force transferred to the rupture. Since the area of the hole is much smaller than the outer (inner? The part under the skin is what I’m talking about) surface area of the pimple, the pressure is much higher.

Am I making any sense? It’s been a while since I’ve taken any physics, and I can’t recall pimple-popping as being on any of my exams.

6

Just as well. It’d leave nasty splotches on the paper.

Ahem. Being serious … what you say seems plausible. Perhaps, the next time I gently probe a suspicious red mark on my person, I should have measuring tools on hand to quantify the force used, the diameter of the aperture, and the (ahem) mass, volume, and velocity of the expelled material.

(The worrying thing is, having done that search earlier, I can think of half a dozen people who’d probably consider this their idea of fun.)

7

My first thought upon seeing the title? Was he looking at porn?

It sounds like infection of some kind, a hair can become ingrown and infected, so it might be pus, infection of some kind. Put some peroxide on it…and pull up your pants…they are pooled around your ankles, right?
Margo

8

Not while I’m at work, no. We have a relaxed dress code, but not quite that relaxed.