Symptoms, Causes, Treatment, and More

Gnat bites are insect bites that cause small red bumps to form on the skin. Sometimes called black flies or midges, gnats are small, flying insects that live near rivers and streams. As with mosquitos, female biting gnats need blood to survive, but unlike mosquitos, gnats can’t bite through clothing. Gnat bites account for less than 0.1% of emergency room (ER) visits, although the exact number is unknown.

In addition to causing red bumps, gnat bites can cause itchiness and pain. Generally, these bites do not pose severe health risks, and most people can manage the symptoms at home. However, some people may experience an allergic reaction to gnat bites, which could require medical help.

The symptoms of gnat bites are consistent with those of an allergic reaction, mosquito bite, or sting. Symptoms arise after the bite and tend to include:

• A small, red bump on the affected skin
• Itchiness
• Redness in the skin around the affected area
• Swelling or fluid buildup around the affected area
• The development of blisters around the bite, which is a rarer symptom

In rare cases, gnats carry and can spread a nematode—a very small, parasitic worm—known as Mansonella ozzaqrdi. Mostly found in tropical areas or areas with hotter climates, M. ozzaqrdi embed themselves in the bloodstream or tissues. Most often, this infection is asymptomatic. However, some people with the infection have reported certain symptoms, including:

• Fever
• Joint pain
• Headache
• Cold or cool legs and feet
• Skin rash
• Swollen lymph nodes (small ovular structures in the body that are part of the immune system)  

When a gnat bites the skin, it uses the jagged teeth-like edges of its mandible (jaw), which sticks out (similar to a mosquito). As the gnat makes a tiny cut in the skin, it introduces saliva to the area to prevent blood clotting. The blood pools, and the gnat drinks it, which takes about 2-5 minutes. The saliva causes an allergic-type reaction, which leads to swelling, itching, and other symptoms.

Gnats hatch into a larval stage (appearing like worms) before growing wings in their adult phase. Only adult females in the Ceratopogonidae family of gnat species bite. They need the blood to help them lay eggs. They live in coastal areas, swamps, rivers, lakes, or other muddy or wet areas and are most active around dawn or dusk. Requiring warmer temperatures, gnats also tend to appear seasonally during the spring and summer months.

Risk Factors

While everyone is susceptible to gnat bites, certain factors can increase your risk, including:

• Living near or going to a swamp, coastal area, river, lake, or other gnat habitat
• Working on a farm, in a park, or with animals
• Participating in activities like hiking, camping, canoeing, or other recreational water sports

A healthcare provider can typically diagnose gnat bites by looking at them. However, if you have a complication or severe reaction to the bites, your provider may ask about your medical history and current medications or perform certain lab tests.

In some cases, your provider may want to rule out other potential causes of symptoms, including contact dermatitis (allergic skin rash), drug side effects, eczema (a chronic skin disorder), and cellulitis (a skin infection), among other things.

If your healthcare provider suspects an underlying health condition is worsening or mimicking gnat bite symptoms, they may perform the following clinical lab tests:

• Complete blood count (CBC): This test screens for blood components like red and white blood cells and platelets (irregular values detect infection), anemia (low red blood cell count), immune system problems, and other blood disorders.
• Basic metabolic panel (BMP): This test measures levels of glucose (blood sugar), calcium, sodium, and blood urea nitrogen (a waste product) to screen for chronic diseases or kidney problems.
• Liver function: This panel of tests assesses levels of certain proteins and enzymes in the blood to screen for liver problems.
• Coagulation: A healthcare provider will administer a small cut on the skin and assess how quickly your blood coagulates (clots). This helps detect liver problems or blood disorders.
• Creatine kinase: Abnormally high levels of this blood enzyme indicate injuries and diseases of the muscles.
• Urinalysis: Clinical testing and visual analysis of a urine sample allows healthcare providers to screen for signs of infection, kidney problems, diabetes, and other potential causes of symptoms.

Unless you have an allergic reaction, gnat bites go away on their own and typically don’t require care from a healthcare professional. Standard treatments—including home care methods and certain medications—aim to ease itching, swelling, or other symptoms related to the bites.

However, more severe cases and complications may require medications.

Get emergency medical help if you have an allergic reaction. Use an EpiPen (epinephrine injection) if you have one nd call 911 if you experience the following:

• Severe swelling, especially in the face or mouth
• Breathing difficulties
• Slurred speech
• Confusion
• Nausea
• Chest pain
• Sweating

Home Methods

If you’ve been bitten, healthcare providers recommend carefully cleaning and disinfecting gnat bites. Use soap and water to clean out affected areas, and apply an ice pack to help with swelling. Avoid scratching the bites to prevent infection.

Medications

Over-the-counter (OTC) antihistamines, such as Benadryl (diphenhydramine), may help with itching and swelling related to gnat bites.

Another option is hydrocortisone cream, an anti-itch medication. This is available OTC in most drugstores. In more severe cases, your healthcare provider can prescribe a prescription-strength version. You apply these creams directly to affected areas two to four times a day.

The key to preventing gnat bites is to reduce your chances of getting bit. There are several steps you can take to avoid gnats and other insect bites:

• Avoid areas where gnats live, such as rivers, farms, coastal areas, or other bodies of water
• Wear protective, long-sleeve clothing; avoid open-toed shoes
• Treat clothing, camping gear, and boots with permethrin, an insecticide
• Wear insect repellant made with DEET, picaridin, para-mentha-diol (PMD), or oil of lemon eucalyptus (OLE). Note the latter two are unsafe for children under the age of 3
• Don’t go outside around dawn or dusk in areas where there are gnats
• Don’t wear perfumes, colognes, or other scented products; avoid using fragrant shampoos

While rare, gnat bites can cause complications, requiring emergency care or more extensive treatment.

In rare cases, people may have a severe allergic reaction to a gnat bite. This can cause several symptoms, including difficulty breathing, confusion, and severe facial swelling. An allergic reaction is a medical emergency that requires immediate attention.

Another potential complication is skin infection. This can occur from harmful bacteria the gnats might carry or from bacteria spread from scratching the area of the bite too much.

Scratching a bite can also cause pain and skin redness that lasts two days or more, as well as treatment-resistant scabs that swell, discharge fluid, and feel hot to the touch.

Gnat bites cause small, itchy red bumps to form on the skin. They’re caused by female gnats of the Ceratopogonidae family. These small flies live in areas that are damp or near water, such as swamps, forests, farms, rivers, and coastal regions. Though gnat bites are rarely serious, some people can experience allergic reactions or develop an infection.

Treatment for gnat bites includes home management techniques, such as cleaning and icing the area, and OTC or prescribed medications.

You can prevent insect bites by wearing protective clothing, using insect repellants, and avoiding being outdoors during early morning or dusk when gnats are most active.