Gnats are caused primarily by conditions that provide moisture and organic matter for breeding and feeding. Common causes include overripe or rotting fruits and vegetables, excess moisture such as damp soil in houseplants, wet areas from leaks or spills, sweet or fermented liquids, and decaying organic matter like food residue in drains or trash cans. They often enter homes from outside through doors, windows, or cracks, and breed in moist environments like soil, drains, or garbage areas. Indoor houseplants with moist soil are also a frequent source of fungus gnats. These conditions create ideal breeding grounds for gnats, leading to infestations in homes or outdoor areas.
