A study by the Centers for Disease Control and Prevention (CDC) has reported that over 450,000 people in the US may be affected by alpha-gal syndrome (AGS), an emerging allergy to red meat associated with tick bites. It is also known as alpha-gal allergy, red meat allergy, or tick bite meat allergy.
A CDC survey of healthcare providers found that while cases of AGS are increasing in the US, there is limited awareness among healthcare providers about the ‘emerging public health concern’, which has resulted in many going undiagnosed.
What is alpha-gal syndrome?
“Alpha-gal syndrome is an allergic reaction that occurs after consuming red meat, mammalian meat (pork, beef, lamb, rabbit, etc.) or other mammalian products, including milk and dairy,” says Dr Balachandra BV, consultant, pediatric allergy, Manipal Hospital, Old Airport Road, Bengaluru.
“Red meat and mammalian products contain alpha-gal (galactose-α-1,3-galactose), a carbohydrate found in most mammals. Consuming products containing alpha-gal can elicit allergic reactions in some people,” he explains.
In addition, certain medicines like gelatin capsules also contain alpha-gal, which can cause allergic reactions.
Lone star tick: The main culprit
According to the CDC, current evidence suggests that the growing incidence of AGS in the US is primarily associated with the bite of the lone star tick. However, other kinds of ticks haven’t been ruled out yet.
According to Dr Balachandra, the saliva of lone star tick contains alpha-gal, which enters the human body when a tick bites. People with allergic tendencies may start producing antibodies against the sugar molecule, as their body perceives it as a foreign substance.
“When those people get exposed to alpha-gal in the future, the immune system recognises it, inducing an allergic reaction,” he says.
Symptoms of alpha-gal syndrome
Dr Vijay Warad, allergist and clinical immunologist, Sai Allergy Asthma Eye Hospital, Pune, lists some common symptoms of alpha-gal allergy, which include:
- Abdominal pain
- Hypotension (low blood pressure)
- Hives and itchy rashes
- Swelling of the lips, throat, tongue or eyelids
- Nausea
- Heartburn
- Diarrhea
- Cough, shortness of breath or breathing difficulties
- Dizziness
A case study published in the journal Oxford Medical Case Reports describes the case of a 60-year-old Caucasian male who experienced most of these symptoms.
He encountered spontaneous allergic reactions for over three weeks. Besides developing itchy and painful rashes all over his body, he also suffered from abdominal pain, diarrhea, congestion, cough and a sore throat. He was rushed to the emergency department and treated for anaphylaxis after developing shortness of breath and throat tightness.
His medical history didn’t show previous diagnoses of allergies, asthma or atopy, making it difficult to identify the specific triggers for these reactions. However, further investigation revealed that he acquired a tick bite in Arkansas (Southern USA) about two weeks prior to the onset of symptoms, and his diet included beef and dairy products.
How alpha-gal syndrome differs from other food allergies?
While people are aware of allergies to certain foods like soy, shellfish, mushroom, fish and egg, the same about AGS is considerably low.
According to Dr Warad, contrary to most food allergies, the symptoms of AGS usually don’t appear for about two to six hours after consuming red meat or other products containing the carbohydrate.
This delay may hinder people from connecting the symptoms of the allergy to the food that has triggered the allergy.
Dr Balachandra says that in 99 per cent of food allergies, the allergen is a protein component. However, such is not the case for AGS, where the allergen is a carbohydrate.
However, allaying fears, doctors say that not all red meat eaters need to be worried about the allergy, as AGS is seen only among those who experienced a tick bite prior to consuming red meat.
Diagnosis and treatment
The 60-year-old’s laboratory tests indicated an allergic response to alpha-gal sugar, confirming the diagnosis of AGS.
“Tests like component-resolved diagnostics (CRD) can confirm the presence of alpha-gal antibodies in the body,” says Dr Warad. It helps detect IgE (antibody) sensitivity to individual allergen molecules.
He was advised to avoid mammalian meat products and was prescribed an epinephrine autoinjector (EpiPen) and hydroxyzine. However, he continues to eat fish, turkey and chicken with no further reactions or symptoms.
According to Dr Warad, some treatments for allergies include antihistamines, steroids, IV fluids and adrenaline, which are prescribed based on the symptoms and severity.
Takeaways
- Alpha-gal allergy refers to an allergic reaction to red meat and other mammalian products that contain alpha-gal – a sugar molecule. The allergy is mostly associated with a tick bite.
- The saliva of the lone star tick contains alpha-gal, which enters the human body through a bite. People with allergic tendencies start producing antibodies against alpha-gal, and subsequent exposure induces an aggressive reaction.
- Tests like component-resolved diagnostics (CRD) can confirm the presence of alpha-gal antibodies in the body.
- Some treatments for allergies include antihistamines, steroids, IV fluids and adrenaline.
