“No see ums” refers to tiny, biting flies known scientifically as biting midges, primarily belonging to the genus Culicoides. Measuring under 1/16th of an inch, these insects are notoriously difficult to spot. While they are a significant nuisance pest in warm, humid regions like coastal areas and marshlands, they are not considered dangerous to human health in the United States. The primary risk they pose is localized discomfort and potential secondary complications from their bites.
What Happens When a No See Um Bites You?
The bite from a female midge causes an immediate and often intense reaction. Unlike mosquitoes, which pierce the skin, no see um uses razor-sharp mouthparts to slice the skin surface to reach a blood capillary. This causes a sharp, burning sensation that is often more painful than a mosquito bite.
The insect injects saliva containing anticoagulants, which provokes a strong immune response in the host. This reaction typically results in small, intensely itchy red welts or bumps that may appear in clusters. For many individuals, these localized reactions can persist for days, sometimes lasting up to two weeks.
For a small percentage of people, hypersensitivity can lead to more severe reactions. These may include excessive localized swelling, large blisters, or prolonged inflammation that requires medical attention. Excessive scratching breaks the skin barrier, leading to secondary bacterial infections that increase the risk of scarring and prolong the healing process.
Assessing the Risk of Disease Transmission
While biting insects are often vectors for human pathogens, this risk is geographically limited for no see ums. In temperate regions, including the United States, biting midges are not known to spread human diseases. Their bite is primarily a localized irritant and discomfort.
Culicoides species pose a far greater risk to livestock, acting as established vectors for significant animal pathogens. They transmit viruses causing Bluetongue and Epizootic Hemorrhagic Disease in ruminants like cattle and deer. These diseases represent a major economic concern for agriculture.
In specific tropical areas, however, midges pose a confirmed public health risk. Certain species of Culicoides, such as Culicoides paraensis, have been implicated in the transmission of the Oropouche virus in parts of South America. Oropouche virus can cause Oropouche fever, characterized by symptoms like high fever, severe headache, and joint pains.
Preventing Bites and Finding Relief
Proactive measures are the most effective way to avoid the discomfort associated with no see um bites. Since midges are weak fliers, installing fine-mesh screens smaller than the standard 16-mesh size can prevent them from entering homes. Using fans outdoors or indoors also helps deter them by creating air movement they cannot navigate.
Applying insect repellents containing active ingredients such as DEET, picaridin, or oil of lemon eucalyptus provides a chemical barrier on the skin. Since midges are most active during dusk and dawn, avoiding outdoor activity during these peak times significantly reduces exposure. Wearing long sleeves and pants in light colors also helps minimize exposed skin.
For existing bites, the immediate application of a cold compress or ice helps soothe intense itching and reduce swelling. Over-the-counter anti-itch treatments, such as hydrocortisone cream or calamine lotion, can be applied to the welts to manage the immune response. Oral antihistamines can also be taken to reduce the body’s overall allergic reaction and provide systemic relief.