Recently, a friend of mine went to put out my citronella candle before asking me. He blew it out, I didn't catch him in time. I did tell him, after, that the directions say not to blow it out. He asked me why and I said that I didn't know why but that is what the candle says. He then said it doesn't matter and that the candle will be fine.
Smothering a flame is always the safest way to extinguish a candle. Blowing out an oil-based candle like this one can splash hot wax and cause burns. Because of the oil content, you should also never extinguish this candle with water.