Chiggers are parasitic mites found globally. Only the larval stage seeks a host, including humans. Understanding the specific cues these larvae use to locate a meal allows people to take targeted steps to prevent encounters in outdoor environments.
What Exactly Is a Chigger?
A chigger is the common name for the six-legged larval stage of mites belonging to the Trombiculidae family. These larvae are microscopically small, typically measuring less than 0.3 millimeters, making them nearly impossible to see. The subsequent nymph and adult stages are not parasitic, feeding instead on small insects and insect eggs in the soil.
Chigger larvae do not burrow into the skin or suck blood. Instead, they use specialized mouthparts to inject digestive enzymes into the skin. These enzymes break down tissue, and the chigger feeds on the resulting liquefied skin cells. The host’s immune reaction to this enzyme causes the intense, prolonged itching.
Sensory Cues: The Primary Attractors
Chigger larvae rely on physiological and chemical signals to detect a potential host. These cues guide the mite’s questing behavior near the ground.
One significant long-range attractor is carbon dioxide (CO2). Mammals exhale a plume of CO2 that chiggers detect, signaling that a host is nearby. This chemical signal activates the mite and directs its initial movement toward the source.
The mites also use thermal gradients to pinpoint the host once they are closer. Chiggers sense body heat, which helps them distinguish a living host from the surrounding environment. This allows them to move toward the warmest parts of the host’s body after contact.
Moisture and humidity are also important in host selection. Chiggers are highly sensitive to high humidity and moisture, often a byproduct of sweat. This explains why chiggers migrate to areas where clothing is tight, trapping heat and moisture, such as the sock line, waistband, or armpits.
Identifying High-Risk Environments
The sensory cues used by chiggers translate directly into specific environmental conditions where they are most likely to be found. Chiggers thrive in habitats that provide the warmth and humidity they require. They are most active in warm weather, preferring temperatures between 77°F and 86°F.
High-risk environments include areas with dense vegetation, such as tall grasses, weeds, and overgrown brush. The foliage helps trap moisture, creating the humid microclimate chiggers need to survive. They are often found in transition zones, like the border between a manicured lawn and a wooded area.
Chiggers wait on the tips of low-lying vegetation, such as grass blades and low shrubs, in a posture known as questing. They prefer to stay within the first foot of the ground and do not climb high into trees or tall bushes. Areas with leaf litter, near rotting logs, or around natural bodies of water are also common hotspots due to consistent moisture retention.
Actionable Prevention Tactics
Prevention tactics negate the chigger’s attraction cues and create physical barriers to block access to the skin. Wearing the right clothing is a primary defense. Long pants and long-sleeved shirts made of tightly woven fabric should be worn in high-risk areas.
Tucking pant legs inside socks or boots is an effective barrier that prevents chiggers from crawling up the leg. Chemical repellents provide a secondary layer of protection by interfering with the mites’ ability to sense a host. Repellents containing DEET or picaridin can be safely applied to exposed skin.
For clothing and gear, products containing permethrin are highly effective, killing chiggers upon contact and remaining effective through several washings. Permethrin should never be applied directly to the skin. Upon returning indoors, immediately remove all outdoor clothing and wash it in hot, soapy water to kill any hitchhiking mites. A warm, soapy shower with vigorous scrubbing is also recommended after exposure to dislodge any attached larvae.