SOS Allergo · I understand & manage
Alpha-gal syndrome
When a tick bite can cause an allergy to mammalian products
Alpha-gal syndrome (AGS) is a distinctive IgE-mediated allergy. Unlike most food allergies, sensitisation is mainly associated with tick bites. Reactions then occur after exposure to alpha-gal, a carbohydrate found in most non-primate mammals and in some products derived from them.
In this sheet
The most important message
A reaction after a meal containing mammalian products may appear several hours after eating. This unusual delay explains why the responsible food can sometimes be difficult to identify.
What is alpha-gal?
Alpha-gal, or galactose-alpha-1,3-galactose, is a carbohydrate structure found in many mammals. It may be present in beef, pork, lamb/mutton, game, rabbit and various products derived from them.
How does sensitisation occur?
The best-established mechanism is a tick bite. In some people, it leads to the production of IgE directed against alpha-gal. However, being bitten by a tick does not mean that alpha-gal syndrome will necessarily develop.
Who is more exposed?
Risk is mainly related to the likelihood of tick bites. Frequently exposed groups include:
- hunters and people who regularly handle game outdoors;
- forestry workers, wardens, farmers and people working in rural or wooded areas;
- hikers, campers and people with frequent outdoor activities;
- people living in or visiting regions where the relevant ticks are present.
Does the syndrome occur only in the United States?
- United States
- Mainly Amblyomma americanum (Lone Star tick).
- Europe, including France
- Mainly Ixodes ricinus.
- Australia
- Especially Ixodes holocyclus.
- Asia / Japan
- Several species, including some Haemaphysalis and Amblyomma species.
- South America
- Several Amblyomma species have been implicated.
| Region | Ticks mainly associated |
|---|---|
| United States | Mainly Amblyomma americanum (Lone Star tick). |
| Europe, including France | Mainly Ixodes ricinus. |
| Australia | Especially Ixodes holocyclus. |
| Asia / Japan | Several species, including some Haemaphysalis and Amblyomma species. |
| South America | Several Amblyomma species have been implicated. |
Reactions may be delayed and variable
Symptoms often appear 2 to 6 hours after exposure, sometimes during the night after an evening meal. The delay can vary; some offal that is rich in alpha-gal may trigger symptoms more quickly.
Which symptoms can alpha-gal syndrome cause?
- urticaria, itching or redness;
- angioedema;
- abdominal pain, nausea, vomiting or diarrhoea;
- breathing difficulty or wheezing;
- feeling faint, low blood pressure or anaphylaxis;
- in some patients: mainly digestive symptoms, without obvious urticaria.
Why might I tolerate a food once and react another time?
The reaction depends on the amount of alpha-gal consumed, the type of food, individual sensitivity and any cofactors. Severity may therefore vary from one exposure to another.
Do all meats contain the same amount of alpha-gal?
No. The amount and, especially, allergenicity vary with the tissue and product. The table below gives qualitative guidance, not universal thresholds.
- Kidney
- Particularly rich / highly allergenic.
- Other offal
- Often higher risk than muscle meat; varies by organ.
- Beef, pork, lamb, game, rabbit
- Common sources of alpha-gal, even after cooking.
- Processed meats, pâtés, blood sausages
- Check meat, offal, fats and natural casings.
- Lard, tallow, animal fats
- May be relevant for some patients.
- Milk and dairy products
- May contain alpha-gal, but many patients tolerate them.
| Mammalian product | Practical guidance |
|---|---|
| Kidney | Particularly rich / highly allergenic. |
| Other offal | Often higher risk than muscle meat; varies by organ. |
| Beef, pork, lamb, game, rabbit | Common sources of alpha-gal, even after cooking. |
| Processed meats, pâtés, blood sausages | Check meat, offal, fats and natural casings. |
| Lard, tallow, animal fats | May be relevant for some patients. |
| Milk and dairy products | May contain alpha-gal, but many patients tolerate them. |
Cooking does not automatically make a product safe. Alpha-gal is sufficiently heat-resistant for cooked meat, offal or derivatives still to be capable of triggering a reaction.
Where can alpha-gal be hidden?
Meat is not the only possible source. The main aim is to recognise genuinely relevant ingredients of mammalian origin.
View products and ingredients to look for
- Mammalian meat
- Beef, pork, lamb/mutton, game, rabbit.
- Offal
- Kidney, liver, tripe, sweetbreads and other organs; some are particularly allergenic.
- Stocks, broths, meat juices and gravy
- May contain proteins or mammalian derivatives that are not always obvious.
- Sauces
- Check for veal or beef stock, meat juices, broth, gelatin or animal fat.
- Lard, tallow, animal fat
- Direct mammalian derivatives.
- Natural casings
- Often from pigs or sheep.
- Bovine or porcine gelatin
- May be present in food, confectionery and medical products.
- Dairy products
- Discuss according to individual tolerance.
| Product / ingredient | Why consider it? |
|---|---|
| Mammalian meat | Beef, pork, lamb/mutton, game, rabbit. |
| Offal | Kidney, liver, tripe, sweetbreads and other organs; some are particularly allergenic. |
| Stocks, broths, meat juices and gravy | May contain proteins or mammalian derivatives that are not always obvious. |
| Sauces | Check for veal or beef stock, meat juices, broth, gelatin or animal fat. |
| Lard, tallow, animal fat | Direct mammalian derivatives. |
| Natural casings | Often from pigs or sheep. |
| Bovine or porcine gelatin | May be present in food, confectionery and medical products. |
| Dairy products | Discuss according to individual tolerance. |
What about sweets?
Some sweets may contain bovine or porcine gelatin: gummies, jelly sweets, marshmallows, and some jellies or confectionery. This does not mean that every patient with alpha-gal syndrome must avoid all gelatin: tolerance varies.
What about sauces?
A sauce is not risky simply because it is a sauce. Check its ingredients for veal or beef stock, meat juices, broth, gelatin, animal fat or other ingredients of mammalian origin.
Must all dairy products be avoided?
Not routinely. Many patients with alpha-gal syndrome tolerate milk and dairy products. Avoiding mammalian meat is usually the basic dietary measure; avoiding dairy products or gelatin is individualised according to reactions and the level of sensitisation.
Medicines and medical care: what you need to know
Some medicines, excipients or devices may contain alpha-gal or materials of mammalian origin. Risk varies greatly according to the product, route of administration and patient.
Never stop a necessary medicine on your own
Never stop a necessary medicine on your own. Tell doctors, pharmacists, surgeons and anaesthetists about your alpha-gal syndrome so they can check the formulation or device when relevant.
Cetuximab: the best-documented example
Cetuximab is a monoclonal antibody used in oncology, including for some colorectal and head and neck cancers. It is a targeted cancer treatment, not conventional cytotoxic chemotherapy. Alpha-gal on the molecule may be recognised by pre-existing IgE and cause an immediate reaction from the first infusion, unlike the usual delay after food.
Known alpha-gal syndrome and planned cetuximab treatment: the oncology team and allergist must be informed before the infusion.
Other medical products to report or check
- Bovine/porcine gelatin
- May occur in some medicines, vaccines, capsules, plasma expanders or haemostatic products.
- Porcine pancreatic enzymes
- Pancreatin / pancrelipase: a porcine product that should be reported.
- Heparin
- Usually porcine in origin. Reactions are rare; extra care is needed with substantial exposure, particularly high intravenous doses.
- Bovine or porcine bioprostheses
- Some valves and other implants may be made from mammalian tissue.
- Some antivenoms
- May be derived from mammalian antibodies.
- Vaccines containing gelatin
- These are not a general contraindication: check the specific vaccine and context.
| Product | Guidance |
|---|---|
| Bovine/porcine gelatin | May occur in some medicines, vaccines, capsules, plasma expanders or haemostatic products. |
| Porcine pancreatic enzymes | Pancreatin / pancrelipase: a porcine product that should be reported. |
| Heparin | Usually porcine in origin. Reactions are rare; extra care is needed with substantial exposure, particularly high intravenous doses. |
| Bovine or porcine bioprostheses | Some valves and other implants may be made from mammalian tissue. |
| Some antivenoms | May be derived from mammalian antibodies. |
| Vaccines containing gelatin | These are not a general contraindication: check the specific vaccine and context. |
Capsules, glycerin and magnesium stearate: must everything be avoided?
No. Some excipients may be of animal or plant origin, and their industrial source may vary. The mere presence of the name ‘glycerin’ or ‘magnesium stearate’ does not prove that a product contains alpha-gal or will cause a reaction. Avoid automatic prohibition lists and have relevant products checked individually.
How is the diagnosis confirmed?
Clinical history
Look at the delay, meat/offal or hidden products, night-time reactions, tick bites, outdoor activities, cofactors and variation between episodes.
Alpha-gal-specific IgE
This is the main blood test. A positive result does not establish the syndrome on its own: it must fit the clinical history.
Skin tests
Commercial meat skin-prick tests may have low sensitivity. In some specialist centres, adapted tests or prick-to-prick tests with certain foods or offal may be used. They do not replace clinical interpretation.
What about tryptase?
Tryptase does not diagnose alpha-gal syndrome. During a severe reaction, an early tryptase sample may help document anaphylaxis. A baseline tryptase measured later may be useful, particularly after severe or repeated anaphylaxis or if a mast-cell disorder is considered. A normal tryptase does not exclude food anaphylaxis.
What should be avoided?
- Basic avoidance
- Mammalian meat: beef, pork, lamb/mutton, game, rabbit; offal.
- Look for in meals
- Broths, meat juices, stocks, meat sauces, lard/mammalian fats and natural casings.
- According to tolerance / severity
- Dairy products, bovine/porcine gelatin and jelly sweets.
- Report before medical care
- Cetuximab, gelatin-based products, porcine pancreatic enzymes, heparin especially at high doses, and bovine or porcine products/implants.
- No alpha-gal avoidance needed
- Poultry, fish, seafood, eggs and plants.
| Level | Suggested approach |
|---|---|
| Basic avoidance | Mammalian meat: beef, pork, lamb/mutton, game, rabbit; offal. |
| Look for in meals | Broths, meat juices, stocks, meat sauces, lard/mammalian fats and natural casings. |
| According to tolerance / severity | Dairy products, bovine/porcine gelatin and jelly sweets. |
| Report before medical care | Cetuximab, gelatin-based products, porcine pancreatic enzymes, heparin especially at high doses, and bovine or porcine products/implants. |
| No alpha-gal avoidance needed | Poultry, fish, seafood, eggs and plants. |
Prevent further tick bites
Appropriate clothing · repellents · skin checks after outdoor activities · prompt tick removal · suitable prevention for pets. New bites may reactivate alpha-gal reactions.
Common misconceptions
Read common misconceptions and responses
- ‘I have always eaten meat, so I cannot become allergic now.’
- False. The syndrome may develop after years of tolerance.
- ‘Food allergy reactions are always immediate.’
- False: reactions in alpha-gal syndrome are often delayed.
- ‘I must automatically avoid all dairy products.’
- No. Many patients tolerate them.
- ‘Positive alpha-gal IgE means I must avoid every animal product.’
- No. Sensitisation and clinical syndrome must be distinguished.
- ‘All medicines containing magnesium stearate are prohibited.’
- False. The source and clinical relevance vary.
- ‘A reaction is always the same in the same person.’
- False. Amount and cofactors may alter the threshold and severity.
| Misconception | SOS Allergo response |
|---|---|
| ‘I have always eaten meat, so I cannot become allergic now.’ | False. The syndrome may develop after years of tolerance. |
| ‘Food allergy reactions are always immediate.’ | False: reactions in alpha-gal syndrome are often delayed. |
| ‘I must automatically avoid all dairy products.’ | No. Many patients tolerate them. |
| ‘Positive alpha-gal IgE means I must avoid every animal product.’ | No. Sensitisation and clinical syndrome must be distinguished. |
| ‘All medicines containing magnesium stearate are prohibited.’ | False. The source and clinical relevance vary. |
| ‘A reaction is always the same in the same person.’ | False. Amount and cofactors may alter the threshold and severity. |
Key points
Alpha-gal syndrome is an unusual allergy: sensitisation is mainly associated with tick bites, and food reactions may occur several hours after a meal. The aim is not to remove every animal product or every possible medicine, but to identify genuinely relevant exposures, avoid mammalian meat and offal, individualise other avoidance measures and prevent further tick bites.
Download the validated documents (PDFs in French)
The full patient sheet and alpha-gal allergy card are available as two complementary French resources.
You may also want to read
Main references
- CDC. Alpha-gal Syndrome: About; Symptoms; Products That May Contain Alpha-gal; Clinical Diagnosis and Testing; Managing Alpha-gal Syndrome. Mise à jour 2026.
- Commins SP. Diagnosis & management of alpha-gal syndrome: lessons from 2,500 patients. Expert Rev Clin Immunol. 2020;16(7):667-677.
- Platts-Mills TAE, et al. The alpha-Gal epitope - the cause of a global allergic disease. Revue récente sur mécanismes et produits médicaux.
- Morisset M, et al. Anaphylaxis to pork kidney is related to IgE antibodies specific for galactose-alpha-1,3-galactose. Allergy. 2012.
- Fischer J, et al. Travaux européens sur alpha-gal, exposition aux tiques et risque professionnel/loisir.
General information: Information for patients and carers. This sheet does not replace a medical consultation or personalised advice from your healthcare professional.
Scientific review: September 2026 · sosallergo.fr