Some steam inhalers come with special compartments for essential oil pads. These are safe to use with the essential oil of your choice.
Don’t put oil, gel, or anything other than water into a steam inhaler that isn’t designed for that purpose. You’ll clog and break your device if you do.
Make sure to follow the manufacturer's directions exactly before using essential oils.
If you have a pet, make sure the mist is safe for them to breathe in. Some essential oils, such as cinnamon and peppermint, can be toxic to birds, cats, dogs, and other pets when inhaled. It's a good idea to check with your vet before using.