Alpha-gal syndrome (AGS) occurs where an allergy triggered by tick bites leads to a delayed reaction to alpha-gal, a sugar molecule, which is found in mammalian meat (e.g. beef, pork, lamb, goat, rabbit, venison, and their organ meat) and associated products.
Alpha-gal is short for galactose-alpha-1,3-galactose. It’s a type of carbohydrate found in the muscles of non-primate mammals (but not poultry such as chicken or turkey). Alpha-gal allergy affects some people when they are bitten by a tick which carries the alpha-gal molecule in its saliva. When a person eats mammalian meat or mammalian-derived products their body’s immune system can wrongly identify the alpha-gal as a threat and release chemicals such as histamine which go on to cause symptoms.
Associated products include dairy products, gelatin, collagen and lanolin for example, and these can be found in personal care products, some medicines and vaccines. Some people also report reacting to Carrageenan, which is a type of seaweed often used as a thickener in various foods. It is the only plant food that contains alpha-gal.
Although Alpha-gal syndrome is rare in the UK, symptoms can be serious in some cases so it is important to be aware of the risk. Case reports confirm that Ixodes ricinus ticks are causing AGS in UK residents.
Many known cases overseas have been linked to the Lone Star tick which is often found in the southeastern, midwestern, and mid-Atlantic United States. However, cases of alpha-gal allergy have also been reported in many other countries including Australia, Sweden, Italy, Spain, France, Germany, Japan, South Korea, and South Africa, and involve different species of ticks.
Symptoms
Many people who carry anti-alpha-gal antibodies are asymptomatic. Why some people who carry the antibodies develop allergic reactions, while others don’t, is not clear. The syndrome appears to be linked to human genetic factors, possibly past history of allergies and exposure to other allergens, the use of certain medications (e.g. NSAIDS) and alcohol consumption. Adults seem to be affected more commonly than children.
Reactions may fluctuate, differ in severity and vary from person to person. Sometimes for example, only one type of mammalian meat product is involved and some people find they do not react to dairy. Reactions should be observed over a period of time as they may not consistently occur. The symptoms of alpha-gal allergy are often delayed, appearing up to 6-8 hours after eating although quick reactions have also been noted.
- Skin reactions – hives, itching, rash, tingling and swelling of the lips, face, or throat.
- Gastrointestinal issues – nausea, vomiting, stomach pain, diarrhoea.
- Respiratory symptoms – shortness of breath, wheezing, difficulty breathing.
- Other symptoms – dizziness, light-headedness, fainting, drop in blood pressure, tiredness and fatigue.
- Anaphylaxis – in severe cases AGS can progress to anaphylaxis, a life-threatening reaction requiring immediate medical attention.
Most healthcare professionals consider an allergic reaction to be anaphylaxis when it involves difficulty breathing or affects the heart rhythm or blood pressure. Read NHS information on anaphylaxis.
You might be at higher risk of alpha-gal syndrome and more serious reactions if:
- you have travelled to the United States (particularly southern, midwestern and mid-Atlantic regions) or other higher risk areas;
- you have recently been bitten by a tick, or have had multiple tick bites;
- you have spent lots of time outdoors in wooded or rural areas, or environments that could harbour ticks;
- you have already had an allergic reaction;
- you have reacted to a tiny amount of mammalian meat; or
- you have asthma, especially if it is not well controlled.
If you have asthma allergic reactions may be more severe. Make sure you discuss this with your GP or allergy specialist and take any prescribed medicines.
Some patients and researchers have noted a wider range of symptoms not typically associated with Alpha-gal syndrome, such as cardiovascular, emotional, nervous system and motor body system effects. Some patients have had trouble distinguishing some symptoms of Alpha-gal syndrome from Lyme disease symptoms. In addition other patients have gone on to develop mast cell sensitivity alongside Alpha-gal syndrome.
Diagnosis
Medical awareness of Alpha-gal syndrome (AGS) in the UK is growing, but it remains a new and under-recognised condition. Alpha-gal syndrome is diagnosed by a blood test to confirm specific IgE antibody production. It is important to use an NHS accredited laboratory for testing (NHS immunology centres have access to this service). Skin testing is not appropriate and should not be used to diagnose this condition.
The following laboratories are some examples of those that offer testing for alpha-gal IgE:
Other major allergy units can also offer this service so patients should seek guidance from their local specialist unit.
Treatment
Although the initial sensitisation to alpha-gal comes on following a tick bite or multiple tick bites, it is the consumption of alpha-gal that continues the illness in allergic individuals. Careful inspection of product labels by those affected is important to make sure that the relevant triggers are avoided. After abstaining from mammalian meat and associated products over several years, some people find their sensitivities slowly improve and can even resolve.
For severe cases treatment for anaphylaxis, including adrenaline auto-injectors such as EpiPens, may be needed. Other treatments may include antihistamines for milder cases where tolerated.
Please do not hesitate to call 999 when necessary as allergic symptoms can escalate quickly and dangerously in some cases.
Next steps
It is important to contact your GP if you have concerns about alpha-gal syndrome. Patients should be referred to an allergy specialist to confirm the diagnosis and to test which meat and other products should be avoided. Even if symptoms seem mild it is important to confirm a diagnosis because it is hard to know if future allergic reactions could become more severe.