When a tick bite determines what ends up on the table

We know tick bites primarily from Lyme disease. Much less known is that, in rare cases, such a bite can also cause an allergy to mammalian meat. The story does not begin in the stomach, but in the skin.

Why I got stuck on an article about meat allergy

As a skin therapist, I regularly see how an allergic reaction manifests on the outside of the body. Red spots, itching, hives, and swelling are visible signs of an immune system springing into action. Sometimes it is limited to the skin. A more severe reaction can also affect the intestines, respiratory tract, and circulatory system.

That is why I stopped at an article about a little-known allergy: a reaction to mammalian meat that can occur after a tick bite.

I had never heard of it before. Meat has been part of the human diet for thousands of years. It is common knowledge by now that someone can have an allergic reaction to peanuts, pollen, or cats. That a pork chop or meatball can suddenly cause symptoms after a tick bite sounds less obvious.

However, the phenomenon is well documented. It is called the alpha-gal syndrome. It is rare, but scientifically remarkable, because the allergy does not begin in the mouth or in the gut. The first step takes place in the skin.

First the proportions

In the Netherlands, we know the tick primarily as a potential carrier of the bacterium that causes Lyme disease. Every year, people in the Netherlands suffer an estimated 1.5 million tick bites. Approximately 2 out of 100 people develop Lyme disease after a tick bite. That amounts to about 27,000 people per year.

Consequently, Lyme disease after a tick bite is a much greater and better established risk than alpha-gal syndrome.

We do not know exactly how often this meat allergy occurs in the Netherlands. There is no national registry with which the number of patients can be reliably determined. Moreover, there is a difference between people in whom antibodies against alpha-gal are found and people who actually experience symptoms after eating.

The detection of antibodies is called awareness. Alpha-gal syndrome is only diagnosed when someone also has corresponding allergic symptoms. As a result, antibody tests do not automatically reveal how many people are actually sick.

The condition is therefore considered rare and potentially underdiagnosed. The latter does not mean that it will quickly become widespread, but rather that the diagnosis is sometimes missed. Symptoms often only appear hours after a meal, making the link with meat not immediately obvious.

The body does not react to 'meat'

The name meat allergy is understandable, but not entirely accurate. The immune system does not react to meat as a dish. It reacts to alpha-gal, full galactose-alpha-1,3-galactose.

Alpha-gal is a sugar molecule found in the tissues of most mammals. Cattle, pigs, sheep, deer, and rabbits carry it. Humans do not produce the molecule themselves. Neither do birds and fish.

Therefore, chicken, turkey, and fish can generally be eaten by people with alpha-gal syndrome. Beef, pork, lamb, and venison, however, can cause symptoms. Additionally, some people react to organ meat, gelatin, animal fat, or dairy. This varies from person to person.

A false memory of the immune system

A tick bite is not without significance for the body. The skin is damaged and comes into contact with foreign substances. The immune system rightly reacts to this.

While sucking blood, the tick injects saliva into the skin. This saliva contains substances that influence, among other things, blood clotting and the local immune response. As a result, the tick can remain attached for some time without being immediately noticed.

In some people, an allergic sensitivity to alpha-gal develops during or after such a bite. The immune system then IgE antibodies to produce against the molecule. IgE is a type of antibody that is involved in allergic reactions.

In alpha-gal syndrome, the immune system appears to link alpha-gal to the threat posed by the bite. An otherwise harmless sugar molecule thus becomes part of the immunological memory of a potentially dangerous event.

When alpha-gal re-enters the body later, for example through beef, pork, or lamb, the immune system can react. Immune cells then release histamine, among other substances. This can lead to itching, hives, swelling, abdominal discomfort, or shortness of breath.

Where does the alpha-gal come from during the bite?

That mechanism has not yet been elucidated in detail. An obvious explanation is that a tick absorbs alpha-gal during previous blood meals from mammals. After all, ticks feed on the blood of mice, deer, dogs, and other animals, among others.

That is probably not the whole story. Researchers have also found alpha-gall-like structures in ticks and in their secretions. Ticks may be able to form or process these structures themselves. Microorganisms living inside the tick could also play a role in this.

There is still debate regarding the precise origin. There is more clarity on the main point: tick bites can trigger the production of IgE antibodies against alpha-gal in some people. It is likely that the combination of damaged skin, alpha-gal, and the immune-stimulating tick saliva is of particular importance.

A delayed allergic reaction

Another distinctive feature is the delay. With many food allergies, symptoms appear shortly after eating. With alpha-gal syndrome, this usually does not happen until several hours later.

A person may eat meat in the evening and only wake up later in the night with hives, swelling, abdominal pain, nausea, or diarrhea. In more severe cases, shortness of breath, dizziness, or a severe allergic reaction may occur.

Due to this delay, the connection to the meal is not always made immediately. Alcohol, physical exertion, and certain medications can also influence the severity of a reaction. As a result, a meal may cause hardly any symptoms one time, but significantly at another.

Therefore, the diagnosis cannot be based solely on a blood test. The pattern of symptoms, the timing of the reaction, previous tick bites, and detectable IgE antibodies against alpha-gal must be consistent. The assessment should be performed by a physician or allergologist.

The skin as a starting point

Alpha-gal syndrome is interesting because it tells a bigger story about the skin. The skin is not just a protective layer around the body; it is also an active part of the immune system.

The skin constantly distinguishes between harmless stimuli and potential danger. Usually, this is done accurately. Sometimes, an incorrect association is stored, and the immune system continues to react to something that poses no threat in itself.

A barely noticeable bite can thus have consequences that only manifest much later and in a completely different part of the body.

What to do in case of a tick bite?

How do you remove a tick?

Remove the tick as soon as possible. Use pointed tweezers or a tick remover. Grasp the tick as close to the skin as possible and gently pull it out of the skin. If you are using special tick tweezers or a tick card, follow the accompanying instructions.

Do not use alcohol, oil, soap, petroleum jelly, or iodine before removal. This will not help the tick detach. After removal, you can clean the bite site with alcohol or iodine if necessary.

What do you do after removing it?

Note the date and location of the bite on the body. A photo can be helpful to compare changes later. Also check the rest of the skin immediately, as more than one tick may be present.

A small red spot immediately after the bite is usually a normal skin reaction. It generally remains small and disappears within a few days. This does not automatically mean that you have Lyme disease.

When should you contact the GP?

Contact the GP when:

• you are unable to remove the tick;
• the tick has probably been attached for longer than 24 hours;
• a red or dark purple spot or ring appears in the days or weeks after the bite that grows larger;
• you experience symptoms after the bite such as fever, headache, muscle or joint pain, feeling unwell, tingling, or reduced strength;
• you repeatedly suffer from hives, swelling, abdominal discomfort, or shortness of breath after eating products from mammals.

Tell your GP that you have been bitten by a tick, even if the symptoms only appear weeks or months later.

Is a red circle always visible with Lyme?

No. The well-known red ring may develop, but the skin lesion can also consist of a uniformly red or dark purple spot that gradually enlarges. The spot can be located at the site of the bite, but also elsewhere on the body.

Not everyone with Lyme disease develops a recognizable skin lesion. Therefore, do not wait solely for a perfect circle when you start feeling sick after a tick bite.

Are preventive antibiotics necessary?

If the tick has been attached for less than 24 hours, preventive antibiotics are usually not necessary. However, continue to watch for symptoms that could be consistent with Lyme disease.

Do you think the tick has been attached for longer than 24 hours? Then contact your GP. In consultation, a decision can be made between monitoring for symptoms or a single preventive dose of antibiotics. This treatment must be administered shortly after removal and is not suitable for everyone.

Prevent ticks

Ticks do not only live in forests. They are also found in dunes, heathlands, parks, gardens, tall grass, shrubs, and among fallen leaves. They are usually found close to the ground and do not fall from trees.

• Stay on the paths as much as possible during walks.
• Avoid direct contact with tall grass and bushes.
• Wear closed shoes and covering clothing.
• Preferably wear light-colored clothing so that a crawling tick is more visible.
• If necessary, use an insect repellent containing DEET on exposed skin.
• Check the entire skin after spending time in greenery.

Check the backs of the knees, groin, armpits, buttocks, around the waist, behind the ears, and along the hairline. In children, also carefully check the head and neck.

No reason to avoid nature

Alpha-gal syndrome is primarily a remarkable biological phenomenon. It occurs much less frequently than Lyme disease, and neither condition develops after most tick bites.

No one needs to avoid a walk through the woods, an afternoon in the garden, or a holiday in nature. The most practical protection is simple: check the skin, remove a tick as soon as possible, and note the date.

Sometimes good prevention does not lie in complicated measures, but in the habit of taking a good look after a day in the greenery.