Don't know if this is allowed, but Cillian definitely hasn't had work done
So about 10-15 years ago, I did a test by the University of Warwick and I was told that I'm what's called a "super recogniser" -- which is basically exactly what it sounds like. I'm really good at recognising faces.
Part of this skill is noticing the way someone ages, and it makes it really easy for me to spot when someone has had work done, because something essential has changed about their face.
Nothing essential has changed about Cillian's face.
I just wanted to put this up bc I saw a post from about 2-3 weeks ago from someone claiming they were sure he'd had work done bc he looks younger now than he did in Transcendence... no, he doesn't. He looks great for his age -- but he doesn't look younger than he did in 2014. The OP said he had fewer wrinkles now and his skin was glowing (and someone else said he'd had Botox and fillers) -- I think a lot of people overlook the importance of makeup on screen, the red carpet, and "important" press junkets (like for Oppenheimer). If you look at his appearance in junkets for "less important" films like Steve, he looks exactly like he always has, just older. And definitely older than he did in Transcendence.
Obviously I'm not a machine and I've been wrong before (and Botox is not permanent so it is possible I guess that he's had bits of Botox from time to time and he's never been photographed with visible "Botox forehead"... but that would be kinda pointless 😂 also, Botox would be a bizarre thing for a character actor to get, it literally stops an actor from being able to emote).
BUT I would place a large bet on him never having had work done. His face is entirely consistent with the way it's always looked.
Check out the pics I've included, 5 from an interview about Transcendence and 5 from an interview about Steve. He's visibly less lined with more collagen in his face in the Transcendence pics (no signs of Botox or filler in the Steve pics) -- but if you check out the last two pics of him in the Transcendence pics and compare them to the Steve pics, you can even see exactly the same lines forming on his forehead. The man's aged naturally.
Tl:dr: Cillian has aged fantastically. That doesn't mean he's had work done -- and I happen to have a specific skill that helps me identify whether someone's had work done or not.
Oh, edited to add: I chose those pics from the Steve interview to demonstrate that he'd clearly not had work done; but for some reason, when he did the press for Steve, he was observedly slightly thinner than usual, and he has a distribution where any weight loss shows up in his face immediately. His face was much fuller and much more "himself" when he did the premiere for Immortal Man, for example; but I chose the Steve pics bc they were better for proving my point about him not having had work done.
It's still the same at Immortal Man though -- his face hasn't fundamentally changed, and you couldn't make these expressions with Botox: https://youtube.com/shorts/DVltUEiEBKA?is=3meQyQb7bFa5W_xJ