Why Do We Get Rashes? Lessons from Diaper Rash

I saw this patient, a six month old cutie pie little girl.

Her parents brought her into my office because after a few days of diarrhea, her whole little bottom had become bright red.

And of course the parents were convinced that the diarrhea was burning her skin.

That's exactly what it looked like, to be fair.

Now, I know all diaper rashes are not the same because I'm a pediatrician.

So I examined her and I saw that the rash covered the round parts of her bottom, the places that press against the diaper, but the skin folds in her groin were pretty much normal.

Why didn't that part of her skin get burned too? That's actually a clue to what's going on.

The pattern of a rash is crucial when we're trying to figure out what's causing the rash.

And this pattern tells me that this is probably the most common kind of diaper rash there is.

The parents were basically right.

The diagnosis here is irritant diaper dermatitis.

This rash also teaches us something about how skin works.

Most of us think of skin like it's a sheet of plastic wrapping around our bodies, right? A waterproof covering that's there to keep everything in and also keep everything else out.

But it's not like plastic wrap at all.

Your skin is alive.

It's actually the largest organ in your body.

And like some superheroes...

It can rebuild itself.

And your skin communicates with your immune system.

It senses the world around you.

And it performs one of the most complicated engineering jobs we've found in nature.

Seriously, our skin is incredible.

The very top layer of your skin, that's the part you can touch, that's called the stratum corneum.

Scientists like to describe this as like a brick wall.

The bricks are flattened skin cells that have sacrificed themselves for the greater good.