Chiggers are the nearly microscopic larval stage of mites belonging to the family Trombiculidae, which cause intensely itchy bites. These tiny arachnids are often associated with the humid, southern regions of the United States, leading many to question their presence in the Pacific Northwest. Chiggers exist in all 50 states, though their population density and activity vary significantly by region. This information confirms their distribution and describes the specific circumstances under which residents of Washington State may encounter these irritants.
Confirmation and Distribution in Washington State
Chiggers are indeed present in Washington State, although they are not as widespread or numerous as they are in the Southeast or Midwest United States. The state generally experiences a low concentration of these mites compared to warmer, more humid climates, which is why many long-time residents may be unaware of their existence here. The presence of chiggers is noted even in areas of Western Washington, such as near Bellingham, especially during the warmer summer months when conditions are most favorable.
The common North American species, Trombicula alfreddugesi, and other local Trombiculidae species are present across the state. Chigger activity is highly seasonal in Washington, peaking in late spring through early fall when ground temperatures are suitable for their life cycle. While they may not be a pervasive issue statewide, encountering them is possible in specific habitats that meet their environmental needs.
The Chigger Life Cycle and Preferred Habitat
The discomfort from a chigger infestation comes exclusively from the six-legged larval stage, which is the only parasitic phase of the mite’s life cycle. These larvae do not burrow into the skin, contrary to a common misconception. Instead, they attach to a host and inject digestive enzymes that break down skin cells. The mite then ingests this liquefied tissue.
Chiggers prefer habitats that offer cover and moisture, typically found in overgrown, low-lying vegetation like tall grasses, weeds, and wooded edges. They are often abundant in transitional zones between woods and open fields, or in damp areas near streams and ponds. These larvae congregate on small clods of soil or low-growing plants, waiting for a host to brush past, especially when ground temperatures are between 77 and 86 degrees Fahrenheit.
Identifying Chigger Bites and Symptoms
A chigger bite itself is not immediately noticeable because the mite is injecting its enzymes. Symptoms often appear with a delay, typically several hours after the chigger has attached and started feeding. The intense itching, known as pruritus, is the most common symptom and is caused by the body’s reaction to the digestive enzymes and the resulting formation of a feeding tube called a stylostome.
The body’s immune response hardens the surrounding skin cells, creating this stylostome, which the chigger uses to consume the liquefied tissue. The bites appear as small, red welts that can sometimes look like pimples, blisters, or hives. They are frequently clustered in areas where clothing fits tightly, such as around the waistline, ankles, behind the knees, or in the groin area, because clothing restricts the mite’s migration to thinner skin. Itching can be severe for the first 24 to 48 hours, and the lesions may take up to two weeks to fully resolve. Chiggers in North America do not transmit common diseases to humans.
Prevention and Immediate Post-Exposure Care
Preventing chigger bites centers on creating a physical and chemical barrier when entering high-risk environments. Wearing protective clothing, such as long-sleeved shirts and long pants, is recommended. Tucking pant legs into socks or boots can significantly reduce access points. Permethrin, an insecticide, can be applied directly to clothing and gear, but never to the skin, offering a durable repellent effect against mites.
For exposed skin, an EPA-registered insect repellent containing DEET should be applied to deter the larvae. After spending time outdoors in a potentially infested area, removing clothing immediately is crucial. Taking a hot, soapy shower is the most effective immediate care. Scrubbing the skin gently with a washcloth can dislodge any unattached larvae, minimizing the number of bites. To manage the intense itching from bites that have already occurred, over-the-counter anti-itch products like hydrocortisone creams or calamine lotion can be applied. Oral antihistamines can also help alleviate the itching sensation.