Almost everyone knows how bothersome gnats can be. Swarming gnats can ruin a picnic, backyard barbecue or pool party. Inside your home, they can be found fluttering around in the kitchen and bathroom, or buzzing around your face while you’re trying to take a nap or watch your favorite television program. Testing your patience is one thing, but what about gnats that bite? Much more than a nuisance, biting gnats can potentially cause you or your loved ones harm. A closer look at these insects explains how.

A: Many different types of small, flying insects are referred to as gnats. Most of them are considered flies. Not all types of flies or gnats bite. Many species feed on other insects and decaying plant life. So then why do gnats bite humans? Gnats that bite feed on the blood of many mammals, not just people. Usually it’s the female of the species that needs a blood meal before she can lay viable eggs. The most common types of biting gnats or biting flies are buffalo gnats, deer flies, stable flies, biting midges or sand flies.

A: Biting gnats don’t break the skin like mosquitoes. They have four ‟cutters” inside their mouths that slice the skin open so that they can suck your blood. They also inject an anti-clotting agent into the wound that prevents the blood from quickly clotting. This allows them to feed on larger quantities of blood from their unwilling victim.

Consequently, a gnat bite, or a bite from a biting fly, can cause more pain than that of a mosquito. A gnat bite most often occurs on uncovered skin – especially on the head, neck, forearms, hands and legs. The symptoms of a fly or gnat bite will vary depending on which type of insect bit you. In general, you may notice a pinprick or narrow red spot at the site of the bite that will begin to itch. Swelling may develop around the bite and the itching may become more intense.

The more you scratch the area, the higher the risk that the wound becomes infected. If that happens, the swelling will get worse and may contain pus. Some people have an allergic reaction to a gnat’s bite. If the symptoms persist within a few hours from the time you’re bitten, consult with your doctor for advice.

A: Thankfully most species of gnats – even gnats that bite humans – are not known to carry disease vectors. However, the eye gnat has been linked to the transmission of conjunctivitis (pinkeye) in both humans and livestock. There are species of biting flies that can carry a variety of diseases. Deer flies have been identified as carriers of tularemia, and biting midges are known to transmit the Blue Tongue virus to livestock. This virus is a major cause of disease in livestock in the Western United States, but it does not infect humans.