Xjyuk

Various forms of magic exist, and they are used in different ways for different effects. One involves scribing runes onto an object to provide it with magical properties. This allows for enhancement of this o jets in ways that would not be normally possible. A sword that lights on fire for example, or a ring that places a protective barrier around the wearer when activated. This runes are infused with their own power when they were created, with a range of quality. Some are made to last for long periods of time while others fade away after a certain amount of use, in which case they would have to be reapplied or the object replaced completely. In essence, they are like batteries that last for a certain length, and lose power with use.

This extends to magic clothing, specifically made from the materials of animals. Dragon boots and handbags made from creatures can be outfitted with runes to enhance their effects. A handbag that can hold more than it should naturally, or can withstand certain conditions or hold particular powerful magic artifacts without disintegrating. Entire clothing lines have been built which focuses on this for of rune magic.

However, the skin of living things is not suitable for runes. Individuals wishing to power themselves up or give themselves other properties will be disappointed, because living skin is not a good conductor for magic. This sounds like a contradiction.

Why would this be the case?

The body’s natural flow of Chi precludes the addition of further magical effects, somewhat like it being very difficult to build buildings in flowing streams. Any artificial rune will either fail to take or, possibly, disrupt the flow of Chi (with awful side-effects).

This does mean corpses can be rune-ified, as they have no chi.

Animal Material is Magically Processed

One explanation is the animal material needs to be processed in order to make it suitable to be inscribed by a rune, much like how hide is processed to make it into leather. You would have a hard time making boots or handbags out of raw, unprocessed animal hide. The hide may be too weak or too flexible or too uneven or an incorrect shape to be used straight off the animal. In order to make it more useable, animal hide is tanned and processed to make it easier to work with.

In a similar sense, animal material needs to undergo a magical processing, enhancing the material to allow magic to flow through it more easily. For an analogy, think of ice and water, ice being the unprocessed material, water being the processed version:

Its far easier to push your hand into water than it is to push it into a solid block of ice. Heating up the ice turns it into water, allowing your hand to pass through it easily.

By processing the material (heating up the ice) the magic of the rune (your hand) can flow through the material more easily (the animal hide). This magical processing can’t be done on living tissue - it is impossible as, by magically processing the material, you are killing it.

Whilst you might be able to have runes on your body, the process would be a very grisly one. You’d have to have part of your living skin turned into leather and then magically processed before carving a rune into this dead flesh. Not only would this be extremely impractical, it would be an excruciatingly painful process and possibly could be fatal, causing shock in the person or severely damaging vital organs, nerves or arteries.

Magic is stored in the crystal structures like those found in metallic bonds and cation-anion bounds like those salt forms.

These structures can hold magic very well and more perfect the structures are the better the magic storage.

Organic molecules still have structure, but they are much more chaotic than crystal and metal structures.

Thus magic can´t be retained by materials based on them so easily. As you want to know why living things cause a lot of o trouble, organic molecules in still living things are a lot more active, thus making the magic drain unsustainably high.

Concluding everything metals and crystals hold magic best due to their structure. Dead organic molecules work better because they are less active, thus can retain more magic.

The human skin is impermeable to magic. If it weren't, we'd catch fire whenever we approached a fire magic source, drown whenever we approached a water magic source etc.

Magical creatures such as dragons have skins that allow one type of mana to pass through, but not all kinds of mana.

Humans, being humans, cannot be trusted to hanfle magic safely. They have therefore naturally eliminated the mana-permeable epidermis genes from the gene pool through the Darwin Awards.

Some animal skin has magical properties

The skin of animals, such as dragons, may have magical properties which make it more suitable for inscribing runes onto. Their skin conducts magic in a way that human skin or the skin of many domesticated animals simply don’t.

This is like how certain elements on the periodic table conduct electricity extremely well but others do not. A dragon could theoretically have a rune carved into its skin as it better conducts magic than human skin would. However, i doubt a dragon would be willing to let you start slicing into its flesh.

Other mythical creatures may also have magically conductive skin, you may have guilds of hunters who specifically go out to gather the hides of magical monsters to turn into leather to be inscribed with runes. Or, you may have a “dragon ranch” where dragons are raised simply for their meats and hides.

I think the best explanation would be somewhere in the area of autoimmune reaction. Fundamentally, when you enchant something, you change it. In the case of non-living things it wouldn't matter, and there is not much difference whether it is non-organic or organic.

When you try to apply this fundamental change to the part of the living organism, it stops being recognised as a part of itself. Best comparison to the effect of a runic enchantment on the skin would be a failed skin graft at the very least. Inflammation, allergic reactions, the patch of the skin with the runes falling of - that will be the best case scenario. In case of more widely applied runes it would, most likely, result in the death of the subject from toxins.

That means that it can be done in a pinch, for a temporary advantage, but the price of such self-mutilation is too high. Alternatively, it can be used as a particularly gruesome punishment.

Additionally, it means that you would be able to do enchantment on the parts of the organism that are not connected by nerve tissue and blood vessels. Nails, claws and horns on animals, perhaps teeth? Hair would qualify, although I'm at loss how you would be able to make magic patterns on something so thin.