This again depends on the wax used to burn your candles, and also depends very much on the essential or fragrance oil used. At Ralph's Orchard we only use phthalate-free fragrances, as phthalates are nasty plastic chemicals which can be found in almost everything from cosmetics to home fragrance but are known to be damaging to our health. Then there are some people for whom scented candles, or specific scents can induce headaches. This is rare but it does happen and often times does depend on the type and strength of fragrance used. At Ralph's Orchard we make our candles to the maximum strength the wax can contain and the fragrances may therefore set off headaches for some folks. If you suffer from allergies, we always list allergens on the mandatory CLP labels on each home fragrance option. Common allergens found in fragrance and essential oils are linalool and limonene. There are preferable waxes for those with respiratory disease as well, and it helps to choose those with lower soot emissions.