Not so good if you're a pregnant woman and you actually want to keep the baby.

Nitrous Oxide is legal for many purposes.
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The only time I have taken laughing gas was my visit to a dental hospital where the students that day were practicing extractions . i did laugh all the time when I was in the toilet afterwards. However subsequently I feel that I did not need to lose that tooth. It bled a lot afterwards and lost me a good area for crunching and digesting food. It was the thought of pain removal that induced me.
My point is that like any drug this one can also have unexpected and detrimental consequences.

I don't think I've ever tried it, though I hear of people getting it in the dentist chair. Makes sense that it could help - at least temporarily. Interesting!