This article is written by a student writer from the Her Campus at U Toronto chapter.

What determines whether you’re prone to get sick or not, have allergies or autoimmune conditions? Is it all just a natural thing determined by whether your family also gets sick often?

Actually, it’s not just your genetics that are at issue here. Of course, no doubt about it, that’s part of it, but your environment also plays a large role in how well your immune system functions and what chronic conditions you have because of it.

Doctors did a study on identical and fraternal twins and their immune responses by giving them a flu vaccine and measuring their response. Of interest are the identical twins who, if genetics played the only role in immune system formation, should have the same immune response.

However, they found that the pairs produced different amounts of antibodies. This means, their immune response was different. This is because of how large a role environment plays in creating immune diversity.

Encountering Viruses

Many changes within the immune system are caused by encountering different viruses. That single virus can change the actual structure of our immune system and how it functions.

The study on the identical twins showed that encountering the virus called cytomegalovirus, actually changes how our immune system responds in different cases.

Cytomegalovirus is a virus in the herpes family (same family of viruses that can cause chicken pox and cold sores), that a lot of people carry, but doesn’t make them sick in most cases. However, because it essentially just free loads off of us, our immune system is constantly devoting more attention to get rid of it. This makes our immune response to other illnesses weaker.

The presence or absence of the virus within identical twins accounted for 60% of their immune response difference. It’s no doubt that other viruses can do similar things, changing how our immune system responds to different scenarios, thereby making each and every one of ours different.

Much of the immune diversity is actually said to be caused by encountering different microbes, which essentially do the same thing as the cytomegalovirus.

But more than that, this means that where you live can also determine this. Encountering different viruses and allergens also depends a lot on where you live, which means that people in different regions will have differently calibrated immune systems.

Keeping Things Clean

One theory that goes around is the ‘hygiene theory’. No doubt, someone who lives in the Western world has a very different immune system than someone who doesn’t.

If you’re exposed to different allergens and bacteria at an early age, your immune system is said to be better equipped to handle illnesses in the future, contrary to keeping everything extremely clean – what we tend to do in North America and much of the developed world.

The immune system needs to get practice from somewhere. If there’s nothing harmful for it to actually get rid of, it gets bored, for a lack of a better word, and reacts to harmless substances, creating food allergies.

Children have undeveloped immune systems which are more likely to overreact when exposed to different, harmless substances, like nuts for example. In doing this, the body creates histamine to get rid of the allergen as quickly as possible; histamine creates an inflammatory response, which we recognize as anaphylaxis. This is why people like me need an Epi-Pen. But this is less likely to develop if the immune system gets practice, according to hygiene theory.

But can these allergies develop later in life? They can. Adults developing allergies is also more prevalent in developed countries, and some scientists theorize that it’s not just early exposure to bacteria that matters. It’s constant stimulation. Your immune system is really high maintenance and always needs some sort of entertainment. It gets that by encountering different bacteria that won’t happen if everything is spotless.

Encountering bacteria can be the decisive factor in how active or passive each individual’s immune system is, and how it reacts when confronted with a virus. Keeping things too clean is one explanation for why some people develop allergies when confronted with certain triggers and others don’t, although it’s just a hypothesis.

Food Allergies and Diet

I have nut allergies, as do many people who live in North America. However, when I travel to India to visit family, dealing with them is more difficult because of how few people have the same allergies there, and how big of a role nuts play in Indian cuisine.

There is a link between our diet and our immune system, which explains why people in other parts of the world have different kinds of immune responses than we do.

This actually includes less asthma, eczema and allergies than in North America.

In the U.S, there was a test done about the effects of fast food and fruits on immune health. Eating fast food three times a week caused an increased risk of immune conditions like asthma in teenagers and kids. Fruits had the opposite effect and decreased the risk.

Why?

Saturated fats can affect immunity, especially in childhood and can make us more sensitive to the allergens behind asthma and eczema. Fruits, on the other hand, have antioxidants which fight cell damage and boost immune health.

Your diet has an effect on which allergies you can form, and if you form them at all, although it’s a combination of factors. Along with fast foods and fruits, how early allergens are introduced and whether they’re introduced at all plays a role in what we can and can’t eat later in life. What you eat also suggests whether or not you might form skin conditions like eczema or respiratory conditions like asthma.

Differences in diet also account for why people in different parts of the world have different allergies and intolerances – for example, lactose intolerance which is less prevalent in people of European descent.

It’s less genetic and more environment, as it was shown that foreigners who lived in the U.S for more than ten years started to form the same food allergies and immune conditions, while their relatives abroad didn’t. A lot of it is because of food differences.

Your culture tends to affect what you eat, and also how your immune system looks as does where you live.

The Issue with Stress

Chronic stress is said to be especially bad for you when it comes to how well your immune system functions. It does worse things to you than letting you ‘get sick easily’, like most people think.

When constantly stressed, you’ll also have constant inflammation in your body, and as most people know, being stressed lowers your ability to fight infections.

Also you’re constantly stressed, you’ll constantly have a high level of what’s called cortisol in your system. Cortisol is what the body produces to reduce inflammation. This is the reason behind why people who suffer from things like eczema and psoriasis use a topical corticosteroid cream to heal the rashes on their skin and stop the swelling.

If you have a lot of cortisol in your body all the time, your body basically gets too used to it. Your body instead does the opposite of what it’s supposed to when it realizes that the cortisol isn’t working. It produces cytokines which encourage inflammation. Cytokines are associated with a lot of autoimmune conditions where the body essentially attacks itself mistakenly – like lupus and rheumatoid arthritis.

Basically, getting stressed isn’t a good thing and it does more than just making you vulnerable to the common cold. People who are more anxious and constantly stressed will shape their immune systems in different ways, making them more vulnerable to other illnesses, not just the common cold. With each illness, your immune system changes, causing more and more immune variation between you and the person next to you.

This just goes to show that taking a little time to unwind is good for you. More relaxed people tend to have stronger immune systems.

Immune Systems Are Made

Everyone’s immune system is influenced by how they live as well as what genes they inherit.

That’s why even within families, you have a lot of immune variation – with one sibling who has a food allergy that the other doesn’t. Even if there’s no genetic similarity, like with couples who cohabitate, their immune systems are shown to become more similar to each other over time.

They share similar lifestyles.

Understanding our immune systems more can help us prevent different health conditions. But more than that, our lifestyle choices can and do impact us by changing how we respond to illness and even harmless substances down the road.

Sources

5. http://www.everydayhealth.com/allergy/when-allergies-develop-suddenly.aspx

6. https://www.sciencedaily.com/releases/2012/08/120816201618.htm