Brief overview
- Description: Food allergy to red meat and other products containing a specific sugar molecule (alpha-gal), e.g., milk and dairy products.
- Causes: Triggered by the bite of a tick that has previously infested a mammal. The main causative agent is an American tick species, but sometimes it is also European ticks.
- Diagnosis: Blood test for antibodies against alpha-gal, prick test.
- Treatment: avoidance of alpha-gal containing foods, medication for allergy symptoms if needed, avoidance of further tick bites.
- Prognosis: “Meat allergy” may weaken over time as antibodies decrease.
Alpha-gal syndrome: Description
Tick bite as trigger
The allergy is not triggered by the direct consumption of the food, but as a result of a tick bite. Only then does the “meat allergy” develop.
Poultry and fish unproblematic
The consumption of poultry, on the other hand, is unproblematic, since chickens, ducks & Co. do not belong to the class of mammals. Alpha-gal syndrome is therefore not a meat allergy in the true sense of the word.
Those affected can also tolerate fish without any problems.
Alpha-gal syndrome: Causes
If the tick then bites a human, the sugar molecule can enter the human bloodstream. There, the foreign substance alerts the immune system. In the future, the immune system will also react to alpha-gal in food with defense reactions.
American tick as carrier
An American tick species is considered to be the main causative agent: the “Lone Star Tick” (Amblyomma americanum), a species mainly native to the southern USA and Mexico.
How common is Alpha-Gal syndrome in Europe?
Amblyomma americanum does not occur in Europe. However, tick species common in Europe can also transmit the antigen alpha-gal and thus trigger a meat allergy.
In fact, alpha-gal has been detected in the digestive organs of specimens of the common wood tick (Ixodes ricinus). However, there are only a few proven cases of alpha-gal syndrome in humans in Europe.
As ticks conquer more and more regions with climate change, the numbers of affected people are likely to increase in the coming years. The CDC has already observed this for the USA.
In most cases, allergies are triggered by proteins. In fact, in connection with alpha-gal, a sugar molecule was discovered for the first time that can cause strong allergic reactions.
Alpha-gal syndrome: symptoms
- Hives, itchy rash
- nausea, vomiting
- heartburn
- severe stomach pain
- diarrhea
- cough
- shortness of breath or difficulty breathing
- drop in blood pressure
- swelling of the lips, throat, tongue, or eyelids
- dizziness or fainting
Anaphylactic shock: In the course of alpha-gal syndrome, a life-threatening anaphylactic reaction with respiratory distress, circulatory dysregulation and unconsciousness is also possible.
Reactions occur with a time delay
The reason for the delayed onset of symptoms has not yet been conclusively clarified. However, the slow release of alpha-gal during digestion seems to play a role.
The symptoms occur more quickly after eating offal, especially when eating beef or pork kidneys. Here, the allergic reaction usually manifests itself within half an hour to a full hour. More severe reactions and anaphylactic shock are then also more frequent.
Besides the delayed onset of symptoms, there is another difference from many other food allergies. It concerns the amount of allergen needed for allergic reactions:
In food allergies such as peanut or chicken egg protein allergy, eating only trace amounts of the allergen (peanut or chicken egg protein) is sufficient for an allergic reaction. In alpha-gal syndrome, on the other hand, allergen amounts in the gram range are more likely to be required for this.
However, there are individual differences in the amount of alpha-gal that causes an allergic reaction. The severity of this allergic reaction also varies.
In people with a mild form of the syndrome, symptoms sometimes only appear when other factors that influence digestion are added (summation anaphylaxis). Such cofactors influencing the allergic reaction may be, for example:
- physical exertion
- alcohol
- febrile infections
However, whether alpha-gal-containing foods have been heated or otherwise processed before consumption makes no difference with regard to the allergic reaction to them.
Alpha-gal syndrome: Diagnosis
Diagnosing alpha-gal syndrome is not easy: because symptoms are usually delayed for hours after eating allergenic foods, the connection is often not recognized.
Alpha-gal syndrome tests
Antibody test for alpha-gal: If alpha-gal syndrome is suspected, a blood sample can be used to test whether the serum contains antibodies against alpha-gal.
Alpha-gal syndrome: treatment
As with all allergic reactions, the first measure is to avoid the triggers. In the case of alpha-gal syndrome, these are red meat and other alpha-gal containing foods.
Drug therapy
There are no causative drugs for alpha-gal syndrome. However, medications can alleviate the symptoms:
- In acute cases, anti-allergic drugs such as histamine can help.
Hyposensitization, such as exists for pollen allergy sufferers, does not exist. However, the antibodies against alpha-gal seem to decrease by themselves over time.
Avoid tick bites!
Even if you already suffer from alpha-gal symptoms, you should carefully avoid further tick bites. A new bite can intensify or reactivate allergic reactions to Alpha-Gal.
Alpha Gal Syndrome: Prognosis
Can people with alpha-gal syndrome eventually eat meat again? This is not impossible. The antibodies in the blood decrease after some time, unlike in other allergies. The “meat allergy” can therefore weaken.