As people age, it’s natural to want to take the old car in for a tune-up. To give the house a new coat of paint. To spruce up the living room decor.

Bad metaphors aside, it can be tricky to know how to address a friend who’s had cosmetic surgery they haven’t mentioned. What do you say when the first thing you notice about someone you’ve known for years is a physical change? Hint: it’s probably not, “Wow, look at your nose!”

We talked with some experts to find out what not to say in these instances, and what’s helpful to voice instead.

1. “But you looked great even before!”

This is a prime example of something to avoid saying at all costs. “This one basically says, ‘Why the hell did you do it? Huge waste of money,”  Lucio Buffalmano, a social skills, dating and relationships coach and the founder of ThePowerMoves told Considerable.

What to say instead: The way you talk to friends about this sort of thing will often depend on the nature of your relationship. If you’re very close to your friend, it might be appropriate to say something subtle if you’d like to give them space to dive into the conversation as needed.

What do you say when the first thing you notice about someone you’ve known for years is a physical shift? Hint: it’s probably not, “Wow, look at your nose!”

“When the two of you are alone and as if were the most natural thing in the world, you can just say ‘You look so great! Did you do some small retouching?’ ” Buffalmano suggests.

“If you communicate it from a point of view that cosmetic surgery is normal, then you will help them feel welcome and free to open up. And most people welcome the opportunity of opening up. Then look supportive and happy for them. That will remove any possible last hesitation on their side. If you’re interested, also ask from the point of view that you might do the same.”

2. “I wouldn’t do it myself, but I’m happy if you’re happy.”

“This one isolates our friends when they need emotional support the most,” Buffalmano said.

What to say instead: “In general, esthetic improvements should be natural and subtle,” said Inessa Fishman, MD, a facial plastic and reconstructive surgeon at Aviva Plastic Surgery & Aesthetics. “I like it best when my patients hear things like, ‘Did you do something different with your makeup?’ and, ‘You look so well-rested after your vacation!’ after esthetic treatments, both surgical and non-surgical.

“Surgical procedures usually involve a greater downtime, and more involved physical and emotional recovery; less-than-positive comments can really sting and stay with patients for a long time.”

3. “How much did it cost?”

“This can only come after you’ve been speaking for a while and you are also interested in doing the same. Otherwise, it feels judgmental and predatory,” Buffalmano explained.

Say this instead: Knowing you might be similarly interested in a procedure can help your friend relax and dissolve any preconceived notions they might have about judgements you might pass, but only ask about cost if you’re seriously considering a similar procedure and working on weighing your options. Otherwise, it’s simply not appropriate.

4. “Wow, you look so different!”

It’s best never to be too overt. Changing one’s appearance in a permanent way is a deeply personal decision, and everyone who does so has their own specific reasons. Some people may be more open to discussing it than others, who may just want their friends to forget the way they used to look as quickly as possible.

What to say instead: “If a friend or colleague appears to have had cosmetic procedures, I think it’s best to say nothing or stick with the positive and supportive ‘You look great!,’ ” Dr. Fishman explained. “Some patients want to maintain privacy, and may find pointed commentary or probing questions unwelcome. If patients want to be open, they will usually share the details of their treatment. In most cases, I think a neutral or positive approach works best.”

5. “It’s going to take me a while to get used to your new look.”

Ultimately, remember that your friend’s decision to get surgery is just that— their decision. The way you might feel about it matters far less than the way they feel about their own choice.

What to say instead: Karin R. Lawson, PsyD, CEDS-S, a Florida- based psychologist, also errs on the side of less-is-more when it comes to these discussions.

“I would recommend that friends, family and co-workers not acknowledge the cosmetic work that someone has had done,” she said. “I recognize that is not the way of our Western culture — to not comment on someone’s appearance — but I also think that is why so many people struggle with their sense of body image, because appearance is so readily up for grabs by family, friends and the public.”

If someone had cosmetic surgery, it’s often because they were self-conscious about their appearance before the surgery. A great tactic can be focusing on the parts of that person you love that have nothing to do with their appearance.

“I understand that some people want others to comment on their looks, but it can actually be a good psychological shift to help us appreciate that our appearance isn’t all that’s valued or focused on in our relationships,” Dr. Lawson said. “Consider that as an option, instead of worrying about saying the ‘right’ thing. What if it’s OK to not say anything at all?”