Allergy and intolerance
Alpha-gal antilichamen
IgE against a sugar from red meat; part of a meat allergy that only causes symptoms hours after eating.
Everything about this testWhat it measures
Alpha-gal is the short name for galactose-alpha-1,3-galactose, a sugar found in the meat of mammals such as beef, pork, lamb and game. Humans do not make this sugar themselves. After a tick bite, the immune system can start making IgE antibodies against it. This test measures those IgE antibodies in the blood, in kU/l. Unlike most food allergies, this involves a sugar and not a protein, and that explains why the reaction only comes hours later: the sugar first has to reach the blood through digestion.
- Sensitization to alpha-gal: the body has made IgE antibodies against this sugar
- Support in working out a delayed allergic reaction to red meat, together with the history of the symptoms
- A possible explanation for hives or a severe allergic reaction that occurs three to six hours after a meal with meat
High
A value above the cut-off means that you have IgE antibodies against alpha-gal: sensitization. That is not the same as an allergy. If it fits the history, this is alpha-gal syndrome: symptoms after eating red meat that typically only start after three to six hours, usually at night. Symptoms that go with it are itching, hives, abdominal pain and diarrhea, and sometimes a severe allergic reaction with shortness of breath or fainting. Almost everyone with this allergy has previously had a tick bite; in the Netherlands, this is the sheep tick. Poultry and fish contain no alpha-gal and usually cause no symptoms.
Low
A value below the cut-off means that no IgE antibodies against alpha-gal were found. Alpha-gal syndrome is then unlikely. Symptoms after eating meat can also have other causes: an allergy to another protein in meat, a reaction to herbs or marinade, a bowel disorder, or a reaction to something else in the same meal. With a severe reaction without a clear cause, an allergist looks further.
If your result is abnormal
The GP looks at the history: which meat, how many hours later, how often and whether there have been tick bites. With a matching history and a positive result, referral follows to an allergist, who decides on the advice about avoidance and assesses whether emergency medication such as an adrenaline auto-injector is needed. If in doubt, a challenge test can be done in the hospital.
Reliability
A positive IgE result shows sensitization, not allergy: it only says that there are antibodies, not that you get symptoms from meat. With alpha-gal this difference is extra large, because in areas with many ticks, many people have these antibodies without ever having had symptoms. The result can therefore only be interpreted together with the history: if you eat red meat without problems, a positive result does not change that and there is no treatment. This test belongs with a targeted question, usually after an unexplained reaction at night or after a severe allergic reaction.
Limitations
- Sensitization without symptoms is common in people who often get tick bites; only symptoms make it an allergy.
- The reaction only comes three to six hours after eating, so the link with the meal is often not made and the history is harder to assess.
- The amount of meat, alcohol, exercise and anti-inflammatory drugs affect whether symptoms occur; the same meal does not always give the same reaction.
- Laboratories use different measurement methods and cut-off values; results from different labs cannot be compared one to one.
How common is this
Alpha-gal syndrome is rare in the Netherlands and has only become known in recent years. Tick bites, on the other hand, are very common: the RIVM (Dutch National Institute for Public Health and the Environment) estimates that there are about 1.5 million tick bites a year in the Netherlands. Sensitization to alpha-gal is therefore more common than the allergy itself, especially in people who spend a lot of time outdoors in woods and dunes.
Who is this useful for
Useful in people who get symptoms such as itching, hives, abdominal pain or shortness of breath hours after a meal with beef, pork, lamb or game, especially if this happens at night and there have been tick bites in the past. Also with a severe allergic reaction whose cause is unclear. In people who eat meat without problems, the test is not useful: a positive result then does not mean an allergy and does not lead to treatment.
Downsides and risks
- A positive result without symptoms easily leads to meat being left out of the diet unnecessarily, while sensitization without symptoms is not treated.
- A normal result does not rule out a reaction to meat; there are also other causes of symptoms after a meal with meat.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results