Why do our eyes and nose have a different PH?


I got some water in my eyes when showering, and then realised that I don’t understand why it burns my eyes if water goes in, but it doesn’t burn my nose, which is also a mucous membrane? I assume it’s Ph difference, but why is there such a difference in two structures that are really close by?

In: Biology

Well, your brain is literally right next to your skull too, that’s quite a big difference in structure despite being really close by. Distance has no effect on the properties of organs.

As it happens, there is a pH difference between the inside of the nose and the surface of the eye. The eye is slightly alkaline at 7.4, and the nose is slightly acidic at 6.4. However, pH difference isn’t the problem here. Soap is actually quite alkaline, typically in around the 8-10 region iirc, so there’s a bigger difference between your nose and soap than between your eye and soap.

The difference is the value your body places on these organs. Eyes are very, very important. Damage your eyes and you’re fucked. So we’ve evolved to have extremely sensitive eyes that report pain at the slightest contamination – better to be safe than sorry. Your nose is neat, but not that important. Damage to your nose is rarely permanent and even when it is it’s not a huge deal. So, we evolve to be less sensitive to pain in the nose. And you might be thinking, well wouldn’t it be beneficial to know as much about pain as possible? The answer to that is that it’s thought that pain perception is relative, so the body reserves the strongest pains for the most important organs and kinds of damage, so that you never become numb to pain, and can differentiate between high priority and low priority of you suffer multiple damages simultaneously.

Because your nose allows you to breathe and smell, while also using mucus and hairs in your nose to drop dust, dirt, and other debris from getting in. Also, because your eyes are a direct rout to your blood system; which is why medicine can be administered through eye drops.