Candles make me feel safe and cozy at home, especially now that the days are getting shorter and the evenings are getting darker. So if you visit me on any given day, you will probably find at least one candle burning in my apartment, and it's likely to be a scented one.
I wasn't aware of this until quite recently, but most commercial scented candles are made from synthetic ingredients, which can leave toxic or harmful substances in the air when you burn them. For instance, many scented candles contain synthetic fragrances, which are derived from petroleum.
This can be problematic if you burn candles every day, like me. Therefore, I suggest to check all ingredients before you buy a candle, and if you don't know their exact composition, rather refrain from buying it.
Non-toxic candles are made with 100% natural wax and essential oils instead of paraffin and artificial fragrances.
Here are the ingredients you want to avoid:
paraffin wax
stearin wax
artificial fragrances (even if it just says 'fragrance' on the label, this means it's artificial)
phthalates
metal wicks
This is what the label should say:
100% natural wax (soy wax, beeswax, rapeseed wax or coconut wax, no wax blends)
essential oils
paraffin-free
phthalate-free
lead-free wick (e.g. 100% cotton, hemp or wood wick)
Sources