There are a few reasons someone might choose to give up meat — ethical ones, like animal welfare or environmental sustainability; but also nutritional ones, like reducing saturated fat or increasing fiber uptake.

Then there's having a meat allergy, which can make abstention a necessity rather than a choice.

But hang on ... can you really be allergic to read meat?

"Unfortunately, yes," says Dr. Wesley Long, director of diagnostic microbiology at Houston Methodist. "The allergy is to a specific carbohydrate found in red meat, the sugar molecule galactose-α-1,3-galactose — alpha-gal for short."

Alpha-gal is found in many mammals, but not humans. We're exposed to the molecule, though, when we eat red meat, such as beef, pork, lamb or venison.

When a person develops an allergy to this sugar molecule, it's called alpha-gal syndrome. Other names for it include alpha-gal allergy and red meat allergy. As far as food allergies go, it's not a common one. But it can be fairly severe — even life-threatening — especially if a person isn't aware they have it.

How and why exactly does a person become allergic to a carbohydrate in red meat?

What is alpha-gal syndrome?

"Eating red meat isn't the only time a person can be exposed to alpha-gal," says Dr. Long. "Interestingly, the molecule is also found in the saliva of the Lone Star tick, a species predominantly found in the Southeast and Central U.S., but that's recently began moving into the Midwest and even Northeast."

The thinking is that these ticks acquire the molecule after biting an animal that contains alpha-gal, such as a cow or deer.

"With any tick bite, the immune system is going to respond to the irritation caused, as well as to any pathogen the tick may have potentially passed through its saliva," explains Dr. Long. "Ticks are known vectors of many diseases, including Lyme disease, Rocky Mountain spotted fever, Ehrlichiosis and more."

Dr. Long previously studied the bacteria that causes Human Monocytic Ehrlichiosis (HME), called Ehrlichiae chaffeensis — which the Lone Star tick is known to carry.

With alpha-gal syndrome, though, the issue isn't a pathogen in the tick's saliva.

"There can also be an immune response to foreign substances found in tick saliva," says Dr. Long. "In the case of the Lone Start tick, that can mean alpha-gal. It doesn't happen in everyone, but studies show that the immune system can produce high levels of IgE antibodies against alpha-gal after a tick bite."

IgE antibodies are involved in our defense against parasitic infections, but they're also critical players in nasal and food allergies. That is, they're also created in response to allergens, harmless substances that the immune system mistakes as dangerous — like dust or proteins found in peanuts. The job of IgE antibodies is to seek and destroy. If they encounter their target again, these antibodies react by setting off a cascade of powerful inflammatory events known as an allergic reaction.

"If a person has IgE antibodies that target alpha-gal in their system, alpha-gal syndrome results," says Dr. Long. "Any red meat consumed can trigger these antibodies, causing an allergic reaction ranging from mild to severe."

What are the symptoms of alpha-gal syndrome?

Red meat allergy symptoms include:

• Hives or an itchy rash on the skin
• Heartburn and stomach pain
• Diarrhea
• Shortness of breath or difficulty breathing
• Swelling of lips, throat tongue or eyelids
  
  

Like other food allergies, alpha-gal syndrome can progress to anaphylaxis, a life-threatening reaction that requires immediate medical attention. In addition to the symptoms above, signs of anaphylaxis include low blood pressure, nausea and vomiting, weak and rapid pulse and dizziness or fainting.

Unlike other food allergies, however, the reaction doesn't happen immediately. It can take between 2-6 hours after consuming red meat for symptoms to develop, a timetable that can make identifying the syndrome challenging.

"Consult your doctor if you suspect you've developed an alpha-gal allergy," recommends Dr. Long. "A blood test can be used to check for alpha-gal-specific IgE antibodies and aid in diagnosis."

Beware: The allergy isn't limited to red meat

Some refer to it as a red meat allergy, but alpha-gal syndrome can cause an allergic reaction to any animal product that contains the molecule — not just red meat.

According to the CDC, food products or ingredients that may contain alpha-gal include:

• Beef, pork, lamb, venison, rabbit and other mammalian forms of meat
• Cow's milk and cow's milk products
• Gelatins made from beef or pork
• Products containing mammalian fats, like lard, tallow or suet
• Broths, stocks, gravies and bouillons made with meat
  
  

The agency states, though, that not all people with alpha-gal syndrome will react to every food product that contains the molecule. Additionally, there are some non-food products that people with alpha-gal syndrome may need to be cautious about. Work with your allergist to understand which products are of most risk to you.

The best way to prevent a red meat allergy is by preventing tick bites

A person with alpha-gal syndrome won't necessarily have an allergic reaction after every exposure to alpha-gal, and not all alpha-gal containing foods will affect them either. But, unfortunately, people who have the allergy tend to have it for life.

This means that the best way to keep red meat in your diet is to prevent the allergy from ever developing in the first place by reducing your risk of tick bites.

Here are Dr. Long's tick bite prevention tips:

• Know where ticks hide. Ticks typically live in wooded, grassy and brushy areas, overgrown shrubs and leaf piles. But they also can live in backyard habitats, like woodpiles and birdfeeders, and on animals, including pets.
• Dress to protect. When in a tick habitat, especially in wooded, grassy and brushy areas, wear long sleeves, pants and socks. Consider tucking your pants into your socks and wearing a hat and gloves for added protection.
• Don't forget bug spray. Preferably use a 20% DEET-based option, making sure to apply it safely and correctly. (Related: 5 Questions About Bug Spray, Answered)
• Tick-proof your yard and pets. Since ticks can hide in brush and wood, avoid leaving piles of leaves and wood around. If you have pets, ensure they're on a tick preventive.
• Check for ticks. After spending time in an area where ticks may be present, use a mirror to do a full-body check, including in your hair, under your arms, around your ears, around your waist, between your legs and the backs of your knees. Check clothing as well. When in doubt, tumble dry clothing on high heat in the dryer for 10 minutes to kill ticks.
• Shower after spending time outdoors. According to the CDC, showering within two hours of coming indoors has been shown to reduce your risk of getting Lyme disease and may be effective in reducing the risk of other tickborne diseases.
• Remove ticks as soon as possible. Using tweezers, grab the tick at it's head or mouth (as close to your skin as you can), gently pull out and then discard the tick.