Steam inhalation is a safe and by no means unusual procedure to relieve colds so the method should not prevent anyone from trying this remedy. You don't have to dunk your head in boiling water but bend down and hold it close to the pot - only as close as you can. But perhaps the instructions are misleading. I have not tried it myself - I hope I don't have to! It sounds great though, and I'm giving it 5 stars so that people will not get a wrong impression from the 1 star rating.
I am prone to headaches, but I don't think that I want to wrap my whole head in a towel and stick it in boiling water to inhale the steam.