Chemistry, genetics add up to itchy insect interactions
June 30, 2026
By Mary Hightower
University of Arkansas Division of Agriculture
Fast Facts
- Insect bites leave proteins that stimulate immune reaction
- Genetics, body chemistry play role in insect attraction
Frequently asked questions:
(934 words)
DOWNLOAD related art
(Newsrooms: With 06-29-2026-ark-no-see-ums, ‘Research shows tiny midge has huge appetite, impact on some livestock’)
JONESBORO, Ark. — No-see-ums, mosquitoes and ticks are all part of summer’s bargain: they take your blood and you get the itch.
When a bug bites, it injects saliva with proteins that keep the victim’s blood flowing. The proteins trigger the body’s early warning system, setting into action immune cells called mast cells.
“The immune system recognizes these salivary proteins as foreign and mounts a response, beginning with mast cells that release histamine into the surrounding tissue,” said Dr. Sawyer Sparks, a family medicine doctor at the University of Arkansas for Medical Sciences based in Jonesboro.
Histamines are chemicals that set the body’s defenses into action.
“Histamine causes the immediate swelling, redness and itching most people recognize, but histamine is only part of the story,” Sparks said. “A second wave of immune signals — cytokines, along with nerve-activating peptides — drive a deeper, longer-lasting itch by directly stimulating specialized itch-sensing nerve fibers in the skin.
“This is why antihistamines alone often provide only partial relief,” he said. “Much of the itch is driven by non-histaminergic pathways.”
Why do bug bites itch?
The itch is more than just an annoying side effect of an immune response, Sparks said.
“Itch is a built-in defense mechanism. It alerts the body to something on the skin — an insect, a parasite, an irritant — and triggers scratching to remove it,” he said.
Sparks explained that the itch-scratch response, which appears across species, “evolved specifically to combat parasites.”
“There’s a trade-off. Once the immune system is activated, the itch can outlast its usefulness,” he said. “Scratching damages the skin barrier, worsens inflammation and can introduce bacteria, turning a minor bite into a secondary infection.”
Why are no-see-um bites so itchy?
No-see-ums, of the midge genus Culicoides, are particularly sneaky, thanks to the cocktail of saliva ingredients that pour into a victim’s skin as they bite. While the mix varies by species, there will be anticoagulants and vasodilators to keep the blood flowing, plus “it’s going to include analgesics to keep you from feeling as much as possible,” said Emily McDermott, entomologist for the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas Division of Agriculture.
Not that you won’t feel it. Unlike mosquitoes that plunge “something like a hypodermic needle in your skin and find the blood vessel, Culicoides have sawing mandibles, and they will just cut a hole into your skin, and then they drink the blood that is pooling up underneath the skin.”
Sparks said no-see-ums often cause more intense and longer-lasting reactions than other biting insects because of several factors:
- Potent salivary proteins. Midge saliva contains anticoagulants and proteases to break down proteins. Both provoke a strong inflammatory response, including significant mast cell activation, edema or swelling, and vasodilation.
- Delayed immune reaction. Many people develop a delayed hypersensitivity response, with symptoms peaking 24 to 48 hours after the bite rather than immediately.
- Small size, prolonged exposure. At just 1-3 mm long, biting midges are difficult to detect during feeding, allowing repeated or prolonged bites before the host reacts.
“The result is intense, persistent inflammation and itch that can last a week or more,” Sparks said.
What's the best way to treat bug bites?
Sparks said treatment focuses on calming the immune response and relieving itch:
- Cold compresses can reduce swelling and provide immediate relief.
- Topical corticosteroids, such as over-the-counter hydrocortisone for mild reactions, or a mid-potency prescription steroid for more stubborn bites, can reduce the itch.
- Second-generation oral antihistamines, such as cetirizine or loratadine, can be useful for itch relief, though they are most effective against the histamine-driven component.
- Avoid scratching to prevent skin damage and secondary bacterial infection.
Sparks said most bite reactions resolve within a week without medical treatment.
“For more severe or persistent reactions, a short course of a stronger topical corticosteroid is often the most effective approach,” he said. “Antibiotics are not needed unless there are clear signs of infection such as spreading redness, warmth or pus.”
Why do all the bugs find me?
Sparks said some people are consistently more attractive to biting insects than others.
“The primary drivers are chemical, not blood type,” he said. “And the differences are remarkably stable over time.”
These drivers are:
- Body odor and skin chemistry. The strongest predictor of mosquito attraction is the level of carboxylic acids produced by the skin. These compounds are generated bacteria residing in the skin that metabolize sweat, and their composition varies from person to person.
- Carbon dioxide. Exhaled carbon dioxide is a major long-range attractant. People with higher metabolic rates or larger body size produce more carbon dioxide and tend to draw more biting insects.
- Heat and moisture. Mosquitoes detect body heat, including thermal infrared radiation, and humidity from the skin at close range, guiding them to landing sites.
- Genetics. Studies of twins suggest that if you’re a mosquito magnet, chances good that you inherited that characteristic from your parents. Genome-wide association studies have identified locations of genes that determine the intensity of a body’s response to an insect bite — whether you’ll see a large or small welt.
“Blood type is frequently cited as a factor, but the evidence is inconsistent,” Sparks said. “Some studies have found that type O individuals attract more of certain mosquito species, while others have found preferences for type B. These results vary by mosquito species and experimental conditions.”
This article is for general information only and is not intended to be a substitute for professional medical advice, diagnosis or treatment. Contact a doctor or other qualified health care professional if you have questions about symptoms or treatments.
To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit uaex.uada.edu. Follow us on Facebook and Instagram. To learn more about the Division of Agriculture, visit uada.edu. To learn more about ag and food research in Arkansas, visit the Arkansas Agricultural Experiment Station at aaes.uada.edu.
About the Division of Agriculture
The University of Arkansas Division of Agriculture’s mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation’s historic land-grant education system.
The Division of Agriculture is one of 22 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on three campuses.
Pursuant to 7 CFR § 15.3, the University of Arkansas Division of Agriculture offers all its Extension and Research programs and services (including employment) without regard to race, color, sex, national origin, religion, age, disability, marital or veteran status, genetic information, sexual preference, pregnancy or any other legally protected status, and is an equal opportunity institution.
# # #
Media Contact:
Nick Kordsmeier
Nkordsme@uada.edu