I really like how you've approach this, some of the little details just create such a vivid world

skin as bright as that of a baby

in just a few words, you make multi colored skin seem natural, and this feel like a normal procedure people may use to change color, or just brighten up their natural shade. The almost patronizing positive routine of the nurse, this very much feels like a real clinic. The way he deflects his nerves with humor and then focuses on his end goal, Lara. You give Arnav an emotional depth, and then, wow, that ending.

The fact you don't explain his change of mind is brilliant, just as the testimonials sang the praises of DermaTru, so does Arnav now. I feel like there is something in the word choice "host"... it makes me wonder what are these nanites... reading this, it feels as though they could be parasites, rather like the ones that make ants love being infected with them. The nanites might change their hosts skin color, but that's not all they change...

This is so delightfully sinister, and it's simplicity just makes it. The unexplained change of heart, from anxious and uncertain, deflecting his worries, thinking of Lara to get himself through, to happy compliant man, combined with Lara's uncharacteristic reaction. I just love how you've played off the title here. The idea of a person going for a cosmetic procedure, and coming back acting so different, can't help but reflect on why and gosh, it so wonderfully creepy!