Mammalian meat allergy
Mammalian meat allergy or MMA is an allergy to meat, and sometimes also to other animal products such as dairy and gelatine, caused by being sensitised earlier by tick bites. Australia has the highest prevalence of MMA in the world.
Who gets MMA?
MMA is an emerging diagnosis up and down the East coast of Australia, the prime habitat of ticks in Australia. The paralysis tick (Ixodes holocyclus) is the tick species that is responsible for hypersensitivity reactions, such as tick allergy, in Australia, so doctors suspect that paralysis ticks are also responsible for MMA. Paralysis ticks are the most common type of tick on the East coast.
To develop MMA, a person must have first been bitten by a tick. Not everyone who is bitten by a tick will go on to develop MMA, but those who suffer large (greater than 50 mm) itchy skin reactions that may last several days, sometimes with swelling, seem most likely to develop MMA.
People who develop mammalian meat allergy after being bitten by a tick usually do so months after the tick bite.
The symptoms of mammalian meat allergy usually start 3-6 hours after eating the meat or meat product, but can be between 2-10 hours after, sometimes waking a person in the middle of the night. This can make it difficult to link the 2 events, unlike other food allergies which occur soon after eating the food. The delay is because the substance causing the allergy (alpha gal) has to be released from the meat by digestion.
The symptoms of MMA are often severe and includes symptoms of anaphylaxis in up to 60% of cases, which can be life-threatening.
Some of the symptoms that may be experienced are:
- Delayed stomach pain.
- Hives (an itchy raised skin rash doctors call urticaria).
- Difficulty breathing, shortness of breath, wheezing.
- Constriction of the throat.
- Tongue swelling.
Get urgent medical help if you start to suffer symptoms of mammalian meat allergy. Symptoms may worsen rapidly and can be life-threatening.
MMA is caused by a person becoming allergic to a sugar molecule called alpha galactose (shortened to alpha gal), which is present in the meat from most mammals.
A tick seems to acquire alpha gal in its gut or possibly saliva after feeding on a mammal, for example native mammals such as a bandicoot. All stages of ticks (except adult males) need to feed on mammals (including humans) to obtain a blood meal.
It has been suggested that the tick transfers alpha gal into a human when it regurgitates the earlier blood meal into the human, especially if it is squeezed or agitated during removal attempts, but doctors don’t seem entirely sure yet how exactly humans develop the mammalian meat allergy from the tick bite.
To avoid MMA (and other tick related illnesses) doctors now advise people who don’t have tick allergy to kill an attached tick with a freezing spray, so that it doesn’t inject you with its saliva or gut contents. Removing it with tweezers is more likely to result in the tick injecting you with saliva or its contents. See Tick removal.
Tests and diagnosis
There are some blood allergy tests that seem to be positive in most people with mammalian meat allergy. These blood tests can help confirm a diagnosis of MMA.
Your General Practitioner should be able to refer you to an allergy specialist or clinical immunologist who will be able to confirm the diagnosis if that is the case.
Unlike some other allergies, there is no desensitisation or allergen immunotherapy available for mammalian meat allergy or tick bite allergy at present.
Treatment of mammalian meat allergy involves total avoidance of meat from mammals. People who also react to gelatine and dairy need to avoid foods and products containing gelatin or dairy as well. This includes some medical products.
A dietitian with experience in MMA will be able to help you design a balanced diet that keeps you safe. It is especially important to get expert advice if you have gelatine or dairy allergy - the dietitian will be able to help you identify hidden sources of these products and help you find alternatives.
If you develop symptoms of mammalian meat allergy, get medical help immediately. Symptoms may get worse quickly and can become life-threatening.
What meat and other products do I have to avoid?
If you have been diagnosed with MMA, you will need to avoid eating beef, ox, lamb, pork, bacon, ham, venison, deer, veal, goat, buffalo, rabbit and kangaroo and some other meats..
Also off the menu are all sausages - even chicken ones (because the casings are made from beef products) and deli meats, such as salami and offal (e.g. tripe, kidneys and liver).
If you are one of the 10 per cent of people with MMA who are also allergic to gelatine, other meat products, or dairy, you will also need to avoid stock cubes, liquid stocks, Bovril, some confectionery (e.g. marshmallows and Jubes), jelly, jam, potato chips, mammalian milks, yoghurt, cheese and ice cream among other things.
You will also need to avoid some medicines, vitamins and medical products, which have been made with animal products. It is best to consult an allergy specialist and a dietitian experienced in MMA regarding what is safe to eat or use.
Doctors advise that you should wear a medical bracelet warning of your allergy and potentially of allergy to intravenous gelatin colloid - a product used as a blood substitute. People with MMA may also be allergic to cetuximab - a product sometimes used in chemotherapy.
Can I eat chicken and meat from other birds if I have mammalian meat allergy?
People with MMA can normally safely eat chicken, turkey, duck and quail and also fish, shellfish and molluscs, according to tiara (Tick induced allergies and awareness).
How to protect yourself from MMA
You can protect yourself from MMA by avoiding being bitten by a tick - and if you do get an attached tick, by killing it then removing it according to the latest advice (see below).
Take precautions to protect yourself from tick bites.
If you live in a tick-endemic area of Australia, don’t scratch anything you can’t see - it may be a tick and if you disturb it, it will likely inject its saliva into you.
Killing and removing a tick
Australian experts and bodies such as ASCIA (the Australasian Society of Clinical Immunology and Allergy) recommend that if you are not allergic to ticks you ‘freeze’ an adult tick with a product such as Wart-Off Freeze or Elastoplast Cold Spray. These sprays contain ether which freezes the tick, thus immediately killing it and preventing it from injecting its saliva into you. You should then leave the tick in place until it drops off, which it should do in the next 24 hours. These sprays are available from pharmacies in Australia.
If you are allergic to tick bites, you should follow your allergy plan or your doctor’s advice.
Tick removal techniques which use tweezers or special hook-like tools run the risk of the tick injecting its saliva or gut contents into you if it is squeezed or agitated/disturbed. This could expose you to transmissible diseases from the tick, sensitise you to ticks or meat, or If you suffer from tick allergy, risk you having a severe allergic reaction.
ASCIA specifically advises against using tweezers or forceps, because of the risk of people allergic to tick bites having an anaphylactic reaction.
For larval and nymph stage ticks, which are around 1-2 mm and hard to see, experts recommend applying a cream containing permethrin, such as Lyclear. These creams are available from the pharmacy.
2. Sheryl Van Nunen. Tick anaphylaxis and allergies. Australian Doctor 2015: 3 February:
3. Tiara (Tick induced allergies and awareness). Chefs card and MMA allergen card. http://www.tiara.org.au/wp-content/uploads/2016/12/TiARA-MMA-card-1.pdf (accessed Feb 2017).
4. Van Nunen SA et al. An association between tick bite reactions and red meat allergy in humans. Med J Aust 2009; 190 (9): 510-511.
5. Van Nunen S. Tick-induced allergies: mammalian meat allergy, tick anaphylaxis and their significance. Asia Pacific Allergy 2015: 5: 3-16.