When you're forced to deal with a condescending co-worker, the first thing you need to do is understand why their comment bothered you so much. What about what this person said irritated you? You might even consider taking time to write it out. Try to recall exactly what this person said. You’ll probably find that it was a specific word or tone this person used, or the way it was delivered, that set you off. It’s important that you identify this because you need to be able to articulate it when you go talk to the person.

This is not the time to bury it, ignore it, or let it slide. The moment you allow condescending behaviour to happen, you are defining how you are to be treated. People treat us the way that we ALLOW them to treat us. If you don’t want to deal with a condescending co-worker, you have to nip this behaviour in the bud.

So, understand exactly what about their comment bothered you. If you need to, talk it out with someone else before you bring it up to your co-worker. Then, confront your co-worker privately so they are aware of how you feel.