By Dr. Michael Zechmann-KhreisSudden abdominal pain, skin rash or shortness of breath after a barbecue? What sounds like a classic food allergy or histamine intolerance is in some cases something completely different: alpha-gal syndrome (AGS) – an unusual meat allergy. Unlike most food allergies, it often only manifests itself hours after eating. And it has something to do with ticks.
What is Alpha-Gal?
“Alpha-gal” stands for galactose-α-1,3-galactose – a naturally occurring sugar molecule found in the cells of many mammals. In some people, the immune system reacts incorrectly to alpha-gal – not immediately, but with a delayed allergic reaction. Humans do not produce this molecule themselves, so it is not possible to have an allergic reaction to oneself.
How does alpha-gal syndrome develop?
The most common cause is a tick bite. In Europe, the wood tick(Ixodes ricinus, or simply the tick) is under suspicion, in the USA the lone star tick(Amblyomma americanum). During sucking, saliva components of the tick enter the blood. The immune system recognizes alpha-gal-like structures and begins to produce IgE antibodies against them.
If meat or animal fat containing alpha-gal later enters the body, an allergic reaction can occur. You have a meat allergy.
Typical triggers:
- Red meat (beef, pork, lamb, game)
- Offal (liver, kidney)
- Products with animal fat (e.g. gelatine, lard)
- Some dairy products (for sensitive people)
- Medication or capsules with animal ingredients
Symptoms – often delayed:
The special feature: symptoms usually occur 3-6 hours after ingestion.
This makes diagnosis considerably more difficult.
Possible symptoms:
- Reddening of the skin, itching, hives
- Swelling (lips, eyelids)
- Abdominal pain, nausea, diarrhea
- Dizziness, circulatory problems
- Shortness of breath
- In severe cases: Anaphylaxis
Diagnosis of meat allergy:
Suspicion arises from:
1. Typical medical history (history of tick bite, delayed symptoms after meat consumption)
2. Specific blood test for alpha-gal IgE antibodies
3. Exclusion of other causes
Therapy & everyday tips
The most important measure is to strictly avoid all triggers.
This means:
- Avoid red meat and offal
- Be careful with ready-made products and gelatine
- Checking medicines for animal ingredients
- In case of severe allergy: emergency kit with antihistamine, cortisone and adrenaline auto-injector
Special features:
- Delayed reaction: differs from most food allergies
- Degrees of severity vary: Some tolerate small amounts of dairy products, others react to even traces
- Cure possible: In some people, the symptoms disappear after years – if there are no further tick bites
Prevention:
Tick protection (long clothing, repellents) is always advisable, also because of other diseases that can be transmitted by ticks. Search thoroughly after spending time outdoors and remove ticks quickly and completely.
Do you have to become vegan?
It’s often said: “A tick bite makes you a vegan” or “If you’re allergic to meat, you have to go vegan”. But this is not true, because alpha-gal is not found in all types of meat. Poultry and fish, which are not mammals, do not contain this sugar. So you can eat eggs, poultry and fish with confidence.
Alpha-gal syndrome is very rare, but treacherous. The delayed symptoms make it difficult to diagnose, but targeted avoidance of the triggers can completely prevent symptoms. Anyone who experiences unexplained symptoms after eating meat – especially after a tick bite – should think about this form of allergy and have it checked out by a doctor.
Sources
The alpha-gal story: Lessons learned from connecting the dots, Steinke, John W. et al, Journal of Allergy and Clinical Immunology, Volume 135, Issue 3, 589 – 596
Commins, S. P. (2020). Diagnosis & management of alpha-gal syndrome: lessons from 2,500 patients. Expert Review of Clinical Immunology, 16(7), 667-677. https://doi.org/10.1080/1744666X.2020.1782745
Macdougall, J. D., Thomas, K. O., & Iweala, O. I. (2022). The Meat of the Matter: Understanding and Managing Alpha-Gal Syndrome. ImmunoTargets and Therapy, 11, 37-54. https://doi.org/10.2147/ITT.S276872