Gnats also known as midges and blackflies are tiny flies that sometimes form swarms in areas of water and folliage especially during dusk. Their bites are smaller and certainly less potent and irritating than mosquito bites.
There are a wide variety of gnat species. They are a general nuisance, often traveling in large swarms around areas with high moisture such as laws, water gardens, pools, patio areas, puddles and other stagnant waters. Although most species do not bite, their swarms can be an irritant to people who spend time outdoors for various reasons.
Avoiding Gnat bites is very similar to avoiding mosquito bites, and the same repellents may be used. Generally cover up in light colored clothing, use repellent sprays or creams on exposed skin and be especially careful around dusk when gnats like to swarm and bite. If you are camping you may also use repellent devices designed for mosquitoes.