Recent headlines have grabbed attention due to proclamations of the Northward march of the Lone Star tick. Ticks are found through the United States and like to live in warm places (animal fur) close to their favorite meal (blood). Ticks typically feed on rodents, deer, and even the family dog, but can be transferred to humans and bite us as well. Tick bites are typically painless and may not occur for hours after they first latch on to our scalp or body. Ticks are extremely small and hard to find, often hiding in our scalps or mimicking birthmarks.
While most tick bites are painless and often go unnoticed, ticks can cause serious problems for humans by transmitting infectious diseases such as Lyme Disease or Rocky Mountain Spotted Fever. Now, a relatively new form of allergy has also been linked to the bite of the Lone Star tick.
Lone Star ticks are endemic to the Southern United States but have now been identified in Northern states. When ticks bite humans, they expose elements of their saliva to our blood stream. Lone Star tick saliva contains a carbohydrate called galactose-a-1,3-galactose (alpha-gal). Here’s what you need to know:
- Humans do not produce alpha-gal
- Individuals bitten by the Lone Star tick can develop an allergy (IgE) antibody to alpha-gal (but not everyone does)
- Red meat (beef, pork, lamb, venison) contains alpha-gal
- People who are sensitized to alpha-gal after a Lone Star tick bite may then develop an allergy to red meat
- This does NOT cause an immediate allergic reaction to the tick bite itself
Typical food allergy reactions occur almost immediately after ingestion, within minutes or up to 2-3 hours later. Symptoms can include hives, swelling, vomiting, wheezing, or anaphylaxis. If someone has a food allergy, they will react every time they eat it and need to strictly avoid ingestion.
Here’s where the story gets really interesting! The allergic reaction that occurs to red meat in people bitten by the Lone Star tick is delayed. It typically presents 3-6 hours after eating red meat. All of the symptoms are the same, including hives or anaphylaxis. Given the delayed presentation, this allergy is often missed. Adults are most often affected and this can occur suddenly in people who have eaten red meat their entire lives.
It remains unknown how many people have alpha-gal allergy or are at risk for red meat allergy, but most estimates are low, around 1-2% of adults. At this time, this almost exclusively affects people living/visiting the Southern U.S. but given the Northward migration of the Lone Star tick, this will likely change.
At this time, there is no need for anyone currently tolerating red meat to stop eating red meat. There is no connection at all to fish or poultry. A blood test is available to evaluate for allergy to alpha-gal but this is not a screening test and should not be obtained unless a suspected reaction has occurred. However, it is important to for patients and physicians to be aware of this relatively new allergy. If anyone experiences symptoms of an acute onset allergic reaction occurring several hours after eating red meat (or otherwise unexplained), then they should be evaluated for possible alpha-gal allergy.
Ideally, we’ll all try to prevent tick bites in the first place by using bug repellent with at least 20% DEET, picaridin, or IR3535 on exposed skin when hiking or spending time in fields/wooded areas. After coming indoors, the entire body, as well as pets and gear, should be checked carefully for any ticks, which can be removed before a bite has occurred. If a tick is found, it should be removed promptly with tweezers (do NOT burn it off the skin!) by pulling straight upward and not twisting. Any concerns should be discussed promptly with your personal physician.