Why would a guy tell a girl she's dangerous?

I live in the same house as this guy, we talk every day and hang out or watch TV together. I am married but not currently living with my husband, someone made a comment about him liking me so I asked him if he did and he said" I need to be careful around you, I think you might be dangerous" what does he mean by that? He said he doesn't like me like that, so why would I be dangerous?
Why would a guy tell a girl she's dangerous?
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