TickZone

Checked against CDC guidance, sources cited on this page. Last reviewed July 1, 2026. Who makes TickZone

Tick Identification in Illinois

The ticks you are most likely to find in Illinois, with photos and the size, color, and markings that tell them apart. Only the deer tick carries Lyme disease. Below the chart, see which types live in your county.

Female deer tick (blacklegged tick) on a green leaf, with a reddish-orange body, dark shield, and black legs, no white markings

Deer tick

Ixodes scapularis

Carries Lyme

Established in Illinois

Size:
Small, a sesame seed (nymph: a poppy seed)
Look for:
Reddish-orange body, solid dark shield, black legs, no pattern
Carries:
Lyme, babesiosis, anaplasmosis, Powassan
Full deer tick guide →
Female American dog tick with an ornate off-white and brown mottled shield behind the head

American dog tick

Dermacentor variabilis

Established in Illinois

Size:
Larger, an apple seed
Look for:
Brown with an ornate off-white mottled shield
Carries:
Rocky Mountain spotted fever, tularemia (rare)
Full american dog tick guide →
Female lone star tick on a green blade of grass, reddish-brown with a single bright white dot in the center of its back

Lone star tick

Amblyomma americanum

Established in Illinois

Size:
Medium, rounded
Look for:
Reddish-brown; female has a single white dot on the back
Carries:
Ehrlichiosis, STARI, alpha-gal syndrome
Full lone star tick guide →
Female brown dog tick, uniform reddish-brown with no distinct markings

Brown dog tick

Rhipicephalus sanguineus

Found nationwide, the one tick that infests homes and kennels indoors

Size:
Medium, narrow body that tapers toward the head
Look for:
Uniform reddish-brown, no ornate markings
Carries:
Rocky Mountain spotted fever, canine diseases
Full brown dog tick guide →
Female Gulf Coast tick with an ornate silvery patterned shield

Gulf Coast tick

Amblyomma maculatum

A southern tick spreading north into the mid-Atlantic

Size:
Large, bigger than a lone star
Look for:
Silvery ornate markings on the shield, no single dot
Carries:
Rickettsia parkeri spotted fever
Full gulf coast tick guide →
Female Asian longhorned tick, small and uniform reddish-brown with no markings

Asian longhorned tick

Haemaphysalis longicornis

A newer arrival, established in the mid-Atlantic and spreading north

Size:
Small and plain, often found in large numbers
Look for:
Reddish-brown with no markings
Carries:
Mainly a livestock threat; human disease risk under study
Full asian longhorned tick guide →
Rocky Mountain wood tick, brown-bodied with an ornate off-white and gray marbled shield behind the head, resembling the American dog tick

Rocky Mountain wood tick

Dermacentor andersoni

Not established in Illinois

Size:
Larger, an apple seed
Look for:
Brown with an ornate off-white and gray marbled shield
Carries:
Rocky Mountain spotted fever, Colorado tick fever, tularemia
Full rocky mountain wood tick guide →
Pacific Coast tick, brown with a marbled silvery and gray ornate shield and long mouthparts

Pacific Coast tick

Dermacentor occidentalis

Not established in Illinois

Size:
Larger, an apple seed
Look for:
Brown with a marbled silvery-gray ornate shield
Carries:
Pacific Coast tick fever, tularemia
Full pacific coast tick guide →

Illinois establishment is shown for the three ticks CDC tracks by county; the others carry a regional range note. Source: CDC tick surveillance (ArboNET Tick Module), 2025. County surveillance is coarse: “not established” is a lack of records, not proof a tick is absent.

Deer, dog and lone star ticks by Illinois county

These are the three ticks CDC maps county by county, not the only ticks in Illinois: the brown dog, Gulf Coast, and Asian longhorned ticks are in the chart above. Tap a county for its daily tick-risk detail.

CountyDeer tickAmerican dog tickLone star tick
Adams CountyEstablishedEstablishedEstablished
Alexander CountyNot establishedEstablishedEstablished
Bond CountyReportedEstablishedEstablished
Boone CountyEstablishedEstablishedNot established
Brown CountyEstablishedEstablishedEstablished
Bureau CountyEstablishedEstablishedEstablished
Calhoun CountyNot establishedReportedEstablished
Carroll CountyEstablishedEstablishedNot established
Cass CountyEstablishedEstablishedEstablished
Champaign CountyEstablishedEstablishedReported
Christian CountyReportedEstablishedEstablished
Clark CountyEstablishedEstablishedEstablished
Clay CountyNot establishedReportedEstablished
Clinton CountyNot establishedEstablishedEstablished
Coles CountyEstablishedEstablishedReported
Cook CountyEstablishedEstablishedEstablished
Crawford CountyReportedEstablishedEstablished
Cumberland CountyReportedEstablishedReported
De Witt CountyEstablishedEstablishedEstablished
DeKalb CountyEstablishedEstablishedReported
Douglas CountyReportedEstablishedReported
DuPage CountyEstablishedEstablishedEstablished
Edgar CountyReportedReportedNot established
Edwards CountyNot establishedEstablishedReported
Effingham CountyReportedEstablishedEstablished
Fayette CountyEstablishedEstablishedEstablished
Ford CountyNot establishedReportedNot established
Franklin CountyReportedEstablishedEstablished
Fulton CountyEstablishedEstablishedEstablished
Gallatin CountyReportedEstablishedEstablished
Greene CountyNot establishedEstablishedEstablished
Grundy CountyEstablishedEstablishedEstablished
Hamilton CountyReportedReportedEstablished
Hancock CountyEstablishedEstablishedEstablished
Hardin CountyNot establishedEstablishedEstablished
Henderson CountyEstablishedEstablishedEstablished
Henry CountyEstablishedReportedReported
Iroquois CountyEstablishedReportedEstablished
Jackson CountyReportedEstablishedEstablished
Jasper CountyReportedEstablishedEstablished
Jefferson CountyNot establishedEstablishedEstablished
Jersey CountyEstablishedEstablishedEstablished
Jo Daviess CountyEstablishedEstablishedReported
Johnson CountyReportedEstablishedEstablished
Kane CountyEstablishedEstablishedReported
Kankakee CountyEstablishedEstablishedReported
Kendall CountyEstablishedEstablishedReported
Knox CountyReportedReportedReported
Lake CountyEstablishedEstablishedEstablished
LaSalle CountyEstablishedEstablishedReported
Lawrence CountyEstablishedEstablishedEstablished
Lee CountyEstablishedEstablishedReported
Livingston CountyReportedReportedNot established
Logan CountyEstablishedEstablishedEstablished
Macon CountyEstablishedEstablishedEstablished
Macoupin CountyEstablishedEstablishedEstablished
Madison CountyReportedEstablishedEstablished
Marion CountyNot establishedEstablishedEstablished
Marshall CountyEstablishedEstablishedNot established
Mason CountyEstablishedEstablishedEstablished
Massac CountyNot establishedEstablishedEstablished
McDonough CountyEstablishedEstablishedEstablished
McHenry CountyEstablishedEstablishedReported
McLean CountyEstablishedReportedReported
Menard CountyEstablishedEstablishedEstablished
Mercer CountyReportedEstablishedReported
Monroe CountyEstablishedReportedEstablished
Montgomery CountyEstablishedEstablishedEstablished
Morgan CountyEstablishedEstablishedEstablished
Moultrie CountyReportedEstablishedEstablished
Ogle CountyEstablishedReportedReported
Peoria CountyEstablishedEstablishedReported
Perry CountyReportedEstablishedEstablished
Piatt CountyEstablishedEstablishedEstablished
Pike CountyReportedEstablishedEstablished
Pope CountyEstablishedEstablishedEstablished
Pulaski CountyReportedEstablishedEstablished
Putnam CountyEstablishedEstablishedReported
Randolph CountyReportedEstablishedEstablished
Richland CountyNot establishedReportedReported
Rock Island CountyEstablishedEstablishedReported
Saline CountyEstablishedEstablishedEstablished
Sangamon CountyEstablishedEstablishedEstablished
Schuyler CountyEstablishedReportedEstablished
Scott CountyEstablishedEstablishedEstablished
Shelby CountyEstablishedEstablishedEstablished
St. Clair CountyReportedEstablishedEstablished
Stark CountyEstablishedReportedReported
Stephenson CountyEstablishedEstablishedNot established
Tazewell CountyEstablishedReportedEstablished
Union CountyEstablishedEstablishedEstablished
Vermilion CountyEstablishedEstablishedEstablished
Wabash CountyEstablishedReportedEstablished
Warren CountyEstablishedEstablishedNot established
Washington CountyNot establishedEstablishedEstablished
Wayne CountyReportedEstablishedEstablished
White CountyReportedEstablishedEstablished
Whiteside CountyEstablishedEstablishedReported
Will CountyEstablishedEstablishedEstablished
Williamson CountyReportedEstablishedEstablished
Winnebago CountyEstablishedEstablishedReported
Woodford CountyEstablishedReportedNot established

Lone star ticks and alpha-gal syndrome

The lone star tick is established in Illinois in 68 of 102 counties (see the table above). Its bite can cause alpha-gal syndrome, an allergy to red meat.

Do not overlook the tiny ones

Nymph deer ticks are the size of a poppy seed and cause most Lyme cases in Illinois because they are so easy to miss. When you check for ticks, look for the small ones too, especially in June and July.

Illinois tick risk by town

A daily 0–100 tick-risk score for every town in Illinois.

See Illinois →

Tick identification chart

The national chart, plus identification for other states.

All states →

Frequently asked questions

What types of ticks live in Illinois?
Illinois has the deer tick (blacklegged tick), which carries Lyme disease and is established across the state; the American dog tick, which is established; and the lone star tick, which is established and causes alpha-gal syndrome. County-level presence is shown in the table above.
Which Illinois tick carries Lyme disease?
The deer tick, also called the blacklegged tick, is the tick that spreads Lyme disease in Illinois. The American dog tick and lone star tick do not carry Lyme, though they can transmit other illnesses.
Are there lone star ticks in Illinois?
Yes. The lone star tick is established in Illinois, in 68 of the state's 102 counties (Adams County, Alexander County, Bond County and more, listed in the table above). It causes alpha-gal syndrome, a red-meat allergy.
How can I tell these ticks apart?
Use size, color, and legs. The deer tick is small with a reddish-orange body, a solid dark shield, and black legs. The American dog tick is larger and brown with an ornate off-white mottled shield. The female lone star tick has a single white dot on her back. The chart above shows each one.

Tick risk where you live

Tick activity is local and changes daily. Pick your state for tick season dates, the species that live there, and a daily tick-risk score for every town.