I am myself a big supporter of natural methods to deal with any problem. For gnats you have following options:

1. Gnats hate Lavender smell, so you can plant some lavender herbs in your garden to deal with gnats problem if its outdoors.
2. Gnats love Apple cider vinegar. You can make a trap for grants mixing apple coder vinegar with water and dish soap. They will come and visit the trap and get drowned inside it.
3. Gnats hate the smell of Vanilla. You can apply some diluted vanilla lotion on your body to repel gnats.
4. Citronella oil is another thing that most fly breeds including gnats hate the most. You can mix it with water and spray on grants and see them dying instantly.
5. Gnats also die when they come in contact with rubbing alcohol.
6. Beneficial nematodes are microscopic parasites that can kill gnat larvae in the soil without affecting plants.
7. You can sprinkle some borax over the soil to get rid of gnats. Borox is a natural insecticide.

Spero che li troviate utili.

Fonte - 30 modi per eliminare i moscerini dentro e fuori casa