Ticks and Alpha-gal Syndrome

What You Need to Know to Protect Yourself

If I already have alpha-gal syndrome, why do I need to avoid ticks?

If you have alpha-gal syndrome, it is important to avoid additional tick bites. If you are bitten again, your alpha-gal IgE levels can increase (9,12).  If you aren’t bitten your alpha-gal IgE will likely decline over time and with luck, so will your reactivity (12 13). Ticks also transmit infectious diseases.

Tick Species Associated with Alpha-gal Syndrome (AGS)

Ticks associated with, or in some cases suspected of being associated with, the onset of alpha-gal syndrome include:

  • In the U.S., the Lone Star Tick (Amblyomma americanum) appears to be the primary vector of sensitization (1). Other ticks that may possibly be vectors include:
    • The Cayenne Tick (Ixodes cajennense) in southern Texas and Florida (20)*
    • The introduced Asian Longhorned Tick (Haemaphysalis longicornis)** in the eastern U.S. (21)
    • The American Dog Tick (or Wood Tick) (Dermacentor variabilis) in Wisconsin and northern Minnesota (19)***
    • The Black-legged Tick (Ixodes scapularis) (10)† in the eastern U.S.
  • In Europe, the Castor Bean Tick (Ixodes ricinus) (2) is thought to be the primary vector of sensitization. Other ticks that may be vectors include:
    • Hyalomma lusitanicum (46, 52)
  • In Australia, the Australian Paralysis Tick (Ixodes holocyclus) (4) and Ixodes endopalpiger australiensis (5)
  • In Central America, Ixodes cajennense complex (6)
  • In Japan, the Asian longhorned tick Haemaphysalis longicornis (8,51) and Amblyomma testudinarium (9)
  • In Japan and Korea, possibly Ixodes nipponensis (7)
  • In Brazil, possibly Amblyomma sculptum† (7)
  • In the Ivory Coast, possibly Amblyomma variegatum (7)
  • In South Africa, the vector of sensitization has not yet been identified, but may be Amblyomma hebraeum (15)

*Associated with AGS in Central America, but not yet associated with it in the U.S.

**Associated with AGS in Europe, but not yet associated with it in the U.S.

*** Anecdotally associated with AGS  in Minnesota and Wisconsin (19)

† Alpha-gal has been found in the saliva of the Black-legged Tick (Ixodes scapularis) (10) and Amblyomma sculptum (14). As of yet, Black-legged Tick (Ixodes scapularis) have not been associated with AGS.

Other Possible Vectors of Alpha-gal Syndrome 


  • Alpha-gal-modified proteins have been found in the salivary glands of Hyalomma marginatum, Rhipicephalus bursa and cells of Rhipicephalus microplus (3),  but we do not yet know if these species can induce AGS. 
  • It is likely that other species of ticks can also induce alpha-gal syndrome (10), but research is needed to demonstrate this.
  • Differences in tick habitat, questing behavior, and/or anatomy play a role in determining which tick species are primary vectors of AGS (38)

Other Invertebrates

  • There is speculation that chiggers (11) and mites (16) could induce AGS, but this has not been convincingly documented.
  • Limited data suggests that bee and wasp stings can cause a rise in alpha-gal IgE, but we don’t know if they can induce the initial alpha-gal IgE response (12).
  • Preliminary data suggests that Ascaris lumbricoides (hookworms) may be able to elicit AGS (48).
  • Fleas are another ectoparasite which may be associated with AGS, but again, data is preliminary (47).
  • It’s possible that other ectoparasites or endoparasites can sensitize people to alpha-gal (1)(17), in some cases causing low levels of sensitizaton not high enough to produce clinical reactions (18). 

Lone Star Ticks

In the U.S., Lone Star Ticks (Amblyomma americanum) are the primary source of sensitization to alpha-gal (12)

Where Do Lone Star Ticks Live?

  •  Lone star ticks are the most frequent tick found attached to humans in the eastern United States (23).
  • Some of the states where Lone Star Ticks are most numerous include Virginia, Tennessee, North Carolina, Arkansas, Oklahoma, and Missouri (38), but they occur throughout the southern and eastern United States, much of the Midwest (39) and as far north as Canada (22).
  • Lone Star Ticks have recently undergone a rapid expansion in the Northeast and Midwest (23).
  • Due to climate change, habitat disruption, and growing deer populations, the density of Lone Star Tick populations is increasing and their range is expanding (1,22,2324).
  • Lone Star Ticks like dense understory vegetation in young, second-growth woodland habitats. (36).
  • In the MidAtlantic region of the U.S., Lone Star Ticks are often found in xeric forested pine/scrub habitats and along the coast (35).
  • Lone Star Ticks need habitats with specific humidity ranges and are more abundant where invasive plants occur, due to deers’ preference for them (22).


Lone Star Tick distribution. Image provided by the CDC.

When Are Different Stages of the Lone Star Tick Active?

  • Lone Star Ticks are active even in the winter as far north as New Jersey (35), but they are most likely to bite you from early spring through late fall (42).
  • Adults emerge around early spring; their numbers taper off by June or July (35,43,44, 45).
  • Nymph activity picks up a bit later, around April or May, peaks in the summer, and drops off by September  (43,44,45).
  • Larvae are most problematic in the late summer and fall, peaking in July through September, but still around in decent numbers in October in some areas (35,43,44,45). This is when you are most likely to encounter swarms of larvae and receive multiple bites, which is often associated with the onset of AGS (12).
  • Lone Star Tick larvae are extremely tiny and oftern confused with chiggers. 


What Animals Do Lone Star Ticks Feed On?

  • White-tailed deer are the principal host of the Lone Star Tick (36).
  • White-tailed deer are the preferred host of Lone Star Ticks at all stages of development, although larvae and nymphs have also been found on small to medium-sized mammals, passerine birds, and turkeys (35,36,49,50)
  • The tendency of Lone Star Tick larvae and nymphs to feed on large mammals, including humans, can result in hundreds or even thousands (37) of tick bites. This may partly explain why this species is so strongly associated with AGS (38).


What Else Do I Need to Know About Lone Star Ticks?

  • Lone Star Ticks are the most common tick to be found attached to humans in the eastern United States (23).
  • They are very aggressive (42) and  move three times as fast as a Black-legged Tick (41).
  • Unlike some other ticks, which wait for their prey to pass by, Lone Star Ticks are active hunters (40).
  • If you stand or sit near Lone Star Ticks, they will detect your odor and rapidly travel many yards to find you (40).

Besides AGS, What Other Diseases Can Lone Star Tick Bites Transmit?

  • According to the CDC, Lone Star Ticks transmit viruses and organisms which can cause:
  • Human ehrlichiosis
  • Tularemia
  • Heartland virus disease
  • Bourbon virus disease
  • Possibly other tick-borne illnesses
  • Lone Star Ticks are also associated with Southern tick-associated rash illness (STARI).
  • According to the Virginia Department of Health, lone star ticks can also transmit Rickettsia parkeri.

Click here to download a PDF about Lone Star Ticks

For more information about Lone Star Ticks and how to avoid them see Avoiding Ticks.

Frequently Asked Questions about Ticks and Alpha-gal Syndrome

How Do Ticks Induce Alpha-gal Syndrome?

Ticks eject saliva into the bite sites they create in the skin. It’s thought that the saliva triggers an immune response that leads to alpha-gal syndrome (38). The mechanism by which this occurs is still being studied, but it’s believed that AGS is triggered by alpha-gal in ticks’ saliva, possibly in conjunction with adjuvants.

How Long Does a Tick Have to Feed to Trigger AGS?

It is not known how long it can take for ticks to trigger AGS, but it is possible that you are at risk as soon as they bite you and eject their saliva into your skin. For this reason, it is important to avoid tick bites in the first place, not just remove them promptly after they bite you, although you should do that, too.

Do All People Who Are Bitten by Ticks That Can Trigger AGS Get It?

No, most people who are bitten by ticks that can trigger AGS do not develop AGS. Even most people who become sensitived to alpha-gal after being bitten by a tick do not develop clinical alpha-gal syndrome (12).

What Other Illnesses Can I Get from Ticks?

If you are bitten by a tick, you might not just develop AGS. You might also acquire a tick-borne disease.

  • Ticks transmit many diseases.
  • Different tick species transmit different diseases.
  • If you get AGS after a tick bite, don’t assume that all the symptoms you experience afterwards are caused by it.
  • Talk to your doctor about ruling out tick-borne diseases and other illnesses which could be contributing to your symptoms.
  • Learn more about North American tick-borne diseases and the species that transmit them from the CDC.

More Information

Avoiding Tick Bites→

What to Do If You Are Bitten by a Tick→

Ticks and Pets→

Tick Report's Passive Surveillance Database

Visit Tick Report’s Passive Surveillance Database to learn about which species of ticks are being found in your area. 


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