What is an allergy trigger?

Allergy triggers are substances in our environment that cause an allergic reaction. Though some of the symptoms overlap, an allergic reaction is a very specific event in your body and is different from an infection, intolerance, or poisoning.

Everyone’s immune system is a little different depending on what they were exposed to during their lives. Your immune system is constantly at work identifying and disposing of potential invaders, then changing itself to be better prepared in the future. Allergy triggers can change the immune system to become allergic.

Every person has their own unique set of allergy triggers, even if they are only allergic to bug bites. A large study in 2019 found that about 1 in 10 US adults has a food allergy, with about half of those allergies being serious. In addition, the American College of Allergy, Asthma, and Immunology found 60 million Americans get hayfever or respiratory allergies. So let’s take a closer look at allergy triggers, what they are, and some good ways to think about avoiding allergic reactions.

 

What triggers allergies?

Allergens trigger allergies. The scientific word for an allergy trigger is an allergen, which literally means allergy-generating. An allergen is a tiny structure made of protein that triggers our immune system to activate and create antibodies when there isn’t any actual threat. Every form of life from sesame seeds to dogs produces allergens, and they are very very small. Allergens can ride around on fragments smaller than 1 micron in diameter that can easily pass into your blood through your lungs and cause a full-body reaction.

Plants can cause allergies when we inhale pollen or when we eat certain foods. Pollen is usually in the air for at least 9 months out of the year and recent climate changes may be increasing your local pollen count. Pollen allergies are also subject to cross-reactivity, which is when an allergy to one plant’s pollen causes allergies to other plants. Trees like Birch and Aspen are active pollen spreaders in the Spring, grasses take over in the summer, and the allergy season is finished up by weeds in the fall.

Walnuts, pistachios, and almonds

Allergens are proteins, and protein-rich plants foods like nuts from trees (almonds, walnuts, pecans, etc.), peanuts, wheat, sesame seeds, and soy are all considered to be common food allergy triggers. Mold spores, while not plants, are also known to cause allergies.

Insects and other common bugs tend to cause allergic reactions when they bite or when we inhale their leavings. Mosquitos, bed bugs, and many other insects inject allergens under the skin or into the blood when feeding, causing swelling and itching. Dust mites are tiny arachnids that eat dust and live in most homes. Dust mites don’t bite but the waste they leave behind is responsible for dust allergies. Cockroaches also live in most places and can trigger allergies.

Farm animals and pets are known for causing allergies. Around 10% to 20% of people are allergic to pets like cats and dogs. Allergies to more or less every animal we cohabitate with have been reported, from horses to guinea pigs. So-called hypoallergenic pets still cause allergies, but these dogs and cats are bred to spread less allergy triggers due to the type of hair they have.

Milk, eggs, fish, and shellfish are well-known food allergies. In addition to the seeds and nuts above, these protein-rich foods are very common allergy triggers. 

What happens when an allergy is triggered

Allergic reactions are incredibly complex but have some very specific things in common. People who suffer from chronic allergies or who care for someone that does might want to know a little bit about how pollen leads to sneezing. This can help choose doctors and medications.

Allergens stimulate IgE

A disease-causing organism like a virus triggers our immune systems to activate and create antibodies (also known as immunoglobulins) that will recognize that organism to kill it faster in the future. Our immune system has many different types of antibodies that are each tuned for different kinds of invaders. 

The antibodies created in response to allergens are called IgE (immunoglobulin E) antibodies. IgE is thought to help attack large worms and a few other parasites, but when stimulated into production by allergens can be part of the allergy chain reaction. Someone with excessive IgE antibodies is someone with allergies, and is sensitive to at least one allergen.

The incredibly complex process of acquiring an allergy. A) The allergen enters the body. B) An Antigen-presenting cell takes up the allergenic molecule and presents the unique allergens on its surface. The activated antigen presenting cell then migrates to the nearest lymph node. C) T cells recognize the allergen, which differentiate into Th2 cells. D) B cells recognize the allergen through the Th2 cell. E) B cells are activated by allergens. F) B cells differentiate into plasma cells, at which point they would actively synthesize antibodies of IgE from the allergen. G) The IgE antibody that now recognizes the allergen molecule, circulates around the body and attaches to mast and basophil cells. H) When the allergen re-enters the body at a later time it binds to the IgE resulting in an release pre-formed chemicals. One of these chemicals is histamine which causes the 5 symptoms of allergic inflammation: heat, pain, swelling, redness and itchiness. Another mediator is IL-4, which affects more B cells to differentiate into plasma cells and produce more IgE and thus the vicious cycle continues.

IgE releases histamine

In what can only be described as a design flaw, IgE antibodies have a tendency to stick to mast cells, which are the immune cells responsible for holding vast stores of chemical signals for a powerful immune response. When covered in IgE antibodies, mast cells explosively release chemicals like histamine whenever they find the allergen or allergens they are sensitive to. Histamine directly stimulates all of the symptoms we associate with an allergic reaction. Over-the-counter antihistamines work by blocking the signal histamine is trying to send.

Allergies vs. intolerance

The difference between allergy and intolerance is that allergies involve an immune reaction, while intolerance is an inability to digest or otherwise process a food or drug.

One of the most common intolerances is to lactose, in which dairy products cause intense intestinal distress. Lactose intolerance is a result of an inability to produce an enzyme called lactase that breaks lactose down into simpler sugars that can be absorbed by the intestine. Without the enzyme lactose passes through the intestine, causing diarrhea by absorbing water from the blood and causing gas by feeding bacteria in the colon. This issue can be solved by just swallowing some lactase before the lactose. 

Lactose intolerance doesn’t involve the immune system creating IgE in response to an allergen, so isn’t an allergy. A milk allergy is a reaction to the unique cow proteins in the milk, and would involve swelling and other immune responses in the intestine.

Food intolerances are not to be confused with drug intolerances, which refers to an inability to tolerate the side-effects of a drug for any reason. A drug allergy refers to the immune system mounting an attack on the drug’s presence, and comes in the form of allergy symptoms.

How to avoid allergy triggers

When avoiding allergy triggers, it’s always important to keep in mind that even low levels of allergens keep the sensitivity pathways active and can even trigger a full blown reaction. If a plate was used to serve shellfish, for example, it needs to be scrubbed with warm water and soap before it’s safe for someone allergic to shellfish. Even then, make them aware that shellfish was served recently. Here are some easy tips to avoid allergy triggers:

  • Avoid bringing in allergy triggers like pollen and mold spores by keeping a shoeless house or removing outer layers of clothing when getting home.
  • Pay attention to any mild allergic reactions because allergies can get worse with repeat exposure, and take steps to avoid exposure in the future.
  • Vacuum and dust often to reduce both dust mites and other allergens present in dust.
  • Close windows during pollen seasons.
  • Use a neti pot or other nasal irrigator to rinse allergy triggers out of your nose before sleep.
  • Wash bedding and use an air purifier at night to remove bedroom allergy triggers so your immune system can rest when you do.
  • Talk to your doctor about allergen testing and other ways to reduce allergic reactions.

Over the counter antihistamines are the classically effective solutions for allergies. As more and more information about the immune system is uncovered, allergists have developed immunotherapies that can shift the dominance of IgE to other antibodies that don’t trigger an allergic reaction.

 

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Written by

Haldane King is a molecular biologist by education, a statistician by training, and a researcher by nature. He spent 15 years in the market research world helping to grow all types of companies from pharmaceuticals to software to insurance. Haldane has researched the world of air quality, air pollution, and air purifiers at Molekule and now proudly attends to the molekule.com/blog blog.