: How does aloe vera help with sunburns? And why does dry skin burn when you put lotion on it?
In: Biology
Let’s start with the most basic of things: skin is made of cells; layers of dead cells on the top protecting layers of living cells beneath above a layer of reproducing cells that make more and shuffle things up towards the top as the upper layers are used up, so to speak. Mixed into these are other cellular structures, means of getting resources from place to place, and other such things, but right now the big thing to remember is that your skin is made of cells.
Light carries energy; certain sorts of atoms or the molecules they join to form will absorb certain wavelengths of light and react in different ways. This can be a good thing, as for the plants that use red and blue wavelengths of light to drive their photosynthesis, or the way your cells can use UV light to make vitamin D. This can also be nasty; give enough UV energy to your DNA and it can cause certain bits of it to undergo chemical reactions and stick together in ways that make it hard to “read”. Hit your DNA with enough X-rays and it can cause breaks.
Sunburns are a downstream effect of this. Your cells have ways to fix problems that happen in them, but too much damage will still be really bad for them and could be bad for the rest of your body. Because of that, your cells also have mechanisms that cause them to die in controlled ways when the damage they take gets too severe – that way they can get replaced by healthier cells. The reason a sunburn gets red or even blisters is due to that death causing an inflammatory response; the body pumps extra liquid in to get your white blood cells there to clean out the damaged cells and the packets they break into when undergoing controlled cell death. (There’s more to it and a whole lot of signaling, but that’s the basics.) The reason it becomes painful is because it can agitate the receptors you have, such as pain receptors; when the skin is puffy and red and damaged, a touch can set off those pain receptors much more easily.
And _that_ brings us to the answer. Aloe Vera hasn’t really been demonstrated to help treatment of wounds or burns, but it _does_ get those pain receptors to back off a bit, so to speak. It’s hard to point to exactly what the interaction is (though testing continues) because there’s something like seventy-five things in Aloe Vera (vitamins, enzymes, minerals, sugars, anthraquinones, fatty acids, hormones, and more) which might have an impact on your cells, and there’s also the cooling effect of the gel drying on the surface of the skin. Some compounds in it are anti-inflamatory, others may be involved more directly in preventing signals from getting to those pain receptors, essentially. Longer story with citations [here](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2763764/), if you’d like to do more reading.
Similarly, the reason skin lotion burns on dry skin is because it’s seeping into cracks and agitating receptors that typically sense other forms of damage; it’s not a bad thing, it’s just those sensors in the body going “oh gosh, cells got burned here!” because they sense chemicals often exposed when cells get burned, or chemicals close enough to trigger them. It doesn’t burn on not-so-dry skin, I believe, because the same substances can’t get to the things that would go “oh no a burn!” when they ‘saw’ them as easily.
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