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One out of every 2,000 emergency department visits is for a tick bite, according to a recent study from the Centers for Disease Control and Prevention. While a tick bite might not be an emergency in the typical sense, in some cases, it’s wise to seek care quickly. If the tick that bites you is infected, for example, a precautionary dose of antibiotics may help forestall a potential case of Lyme disease.
But not every tick bite warrants such treatment—it’s recommended only if the tick has been attached for 36 hours or longer, if the bite occurred in an area where Lyme disease is common, and if medication can be started within 72 hours of the tick being removed. It’s also recommended only for bites from blacklegged ticks, also known as deer ticks. That’s because Lyme disease is known to be transmitted in the U.S. by only the blacklegged tick and its cousin, the Western blacklegged tick.
Tick bites, however, pose many risks beyond Lyme disease. In the U.S., there are more than a dozen other tick-borne diseases that can make you sick.
“Different types of ticks transmit different germs,” says Thomas Mather, PhD, director of the University of Rhode Island’s TickEncounter Resource Center, which runs TickSpotters, a free tick ID and tracking program in the U.S. He says being able to identify the tick you’ve been bitten by is important for both peace of mind and for avoiding potentially unnecessary treatment for a disease.
It is possible to be bitten by a tick and never discover it, according to the CDC. So even if you haven’t found a tick on you, if you’ve recently been in a tick-infested area and develop flulike symptoms, such as fever, joint pain, and especially a rash, see a doctor. If your doctor suspects a tick-borne disease, it’s important to start treatment early to avoid bigger health problems later.
Here, we’ve provided images and size charts to help you identify several common species of ticks across the U.S., along with the diseases they can transmit. Each of these ticks has three life stages after hatching from eggs: larvae, nymphs, then adults.
According to Mather, some type of tick is active somewhere in the U.S. all through the year. However, “the greatest diversity of types and stages of ticks active is in April, May, and June,” he says. Still, the overall risk of a tick bite remains significant during July, and although it falls throughout the summer, bite frequency spikes again somewhat during late October and early November, according to the CDC’s tick bite data tracker.
On each of the cards below, you’ll find an illustration of an adult female tick. For many species, these are the most likely to feed on humans—though some nymphal ticks also frequently bite. Hover your cursor (or tap, on mobile) to see more information on each species of tick.
If you find a tick on your body, see our instructions for removing it safely.
American Dog Tick
Found: Mainly east of the Rocky Mountains and along the Pacific coast.
Can transmit: Rocky Mountain spotted fever, tularemia.
Notes: These ticks are commonly found along the sides of walking trails and roads, as well as in marshy areas and along the edges of lakes and streams.
Blacklegged Tick/Deer Tick
Found: Widely distributed across the eastern U.S.
Can transmit: Lyme disease, anaplasmosis, ehrlichiosis, babesiosis, Powassan virus, Borrelia miyamotoi disease.
Notes: Although deer tick populations peak in late spring and early summer, adults can remain active throughout the winter, on any day in which temperatures rise above freezing. This tick’s cousin, the western blacklegged tick, inhabits western coastal states and has been found to transmit Lyme disease less frequently.
Lone Star Tick
Found: Across the eastern U.S., but especially in the South.
Can transmit: Ehrlichiosis, Heartland virus, Bourbon virus, Southern tick-associated rash illness.
Notes: A bite from this tick can sometimes induce an allergy to red meat. Scientists describe the lone star tick’s hunting style as “aggressive,” and every life stage of this tick—adults, nymphs, and larvae—will bite humans.
Brown Dog Tick
Found: All 50 states.
Can transmit: Rocky Mountain spotted fever.
Notes: Although these ticks sometimes bite humans, they mainly feed on dogs. Unlike many other U.S. tick species, brown dog ticks can live indoors, in people’s homes and dog kennels, for example. They sometimes cause severe infestations.
Gulf Coast Tick
Found: Southeastern and Mid-Atlantic states, southern Arizona.
Can transmit: R. parkeri rickettsiosis, a form of spotted fever.
Notes: Despite their name, Gulf Coast ticks also tolerate dry conditions surprisingly well—better than many other types of ticks, which tend to prefer humid environments.
Rocky Mountain Wood Tick
Found: Rocky Mountain states and areas of southwestern Canada.
Can transmit: Rocky Mountain spotted fever, Colorado tick fever, tularemia.
Notes: These ticks can be difficult to distinguish from American dog ticks. According to one study, they tend to appear more frequently in areas with abundant sagebrush.
For more information on the diseases transmitted by ticks, see our guide to tick-borne diseases.
Editor’s Note: This piece has been updated to reflect that brown dog ticks are found in all 50 states and to include new data from the CDC about tick bite frequency.