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Alyssa Simpson RD, CDE, CLT
Alyssa Simpson

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Sibo Doctor Approved
certified gastrointestinal nutritionist
Sibo Doctor Approved
certified gastrointestinal nutritionist

Is Food Making You Sick? How to Tell the Difference Between a Food Intolerance, Allergy, and Sensitivity

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If you’re dealing with IBS or SIBO, there are likely foods you avoid at all costs. They may taste good. They may feel good going down. But, you know you’re going to pay for it later.

Your symptoms may show up as digestive issues, hives, or even life-threatening allergic reactions. Many people (especially if you have an underlying condition like IBS) react badly to certain foods. But, the type of reaction depends on exactly what’s happening in your body.

Not all food issues are created equal.

If you’ve got an EpiPen rattling around in your purse, you’re dealing with a food allergy. And some of these can be life threatening.

But some people react negatively to foods without actually being allergic to them. 

Food reactions come in three forms: intolerances, sensitivities, and allergies. If you go down a google rabbit hole of these three terms, you’ll find some disagreement on what each one means. But in my practice, when I refer to sensitivities and allergies, I’m talking about foods that stimulate a reaction in the immune system. Food intolerances happen when you are unable to effectively digest a particular food. 

Which are you dealing with? Let’s dig in and find out.

Food Intolerances

Food intolerances happen when you have trouble digesting a particular food. Let’s take lactose as an example. Many people are “lactose intolerant”. This means they don’t produce the enzyme (lactase) necessary to properly digest lactose (a sugar found in milk).

If you are lactose intolerant, your body lacks a key factor needed to digest milk. So when you consume something with lactose, you don’t digest it well and you develop digestive symptoms. 

Another common food intolerance is FODMAP intolerance. FODMAPS are a group of sugars that some people have difficulty digesting. If you’d like more information on FODMAPS and how to tell if you need to consider a low FODMAP diet, check out this article.

Sucrase-Isomaltase Deficiency, or CSID is a deficiency in the enzyme sucrase-isomaltase, which affects a person’s ability to digest certain sugars and starches. If you have CSID, your body is unable to break down the sugars sucrose (found in table sugar and fruits) and maltose (found in certain grains).

The symptoms of food intolerance are your body’s way of sending you the message that something is wrong. But, this isn’t an immune response. In fact, in a food intolerance, your immune system isn’t involved at all. Your body is just having trouble processing this particular type of food.

If you have IBS, you likely have food intolerances. In fact, the IBS network reports that most people with IBS have food intolerances

When it comes to food intolerances, the severity of your symptoms is affected by the amount of the food you consume. If you are lactose intolerant and have just a tiny bit of lactose, it won’t affect you nearly as much as if you eat a big chunk of soft cheese and wash it down with a glass of milk.

Food intolerances can be hard to pin down. Often the symptoms don’t show up for several hours. So it isn’t always easy to figure out what the offending food actually was.

Your best bet at pinning down your food intolerances is to keep a food journal where you write down foods, serving sizes, and reactions you have throughout the day. Then you and your practitioner can do some detective work to look for patterns and figure out the foods that trouble you.

Here are some symptoms to watch out for if you think you have a food intolerance:
  • Bloating
  • Excess gas
  • Abdominal pain
  • Upset stomach
  • Diarrhea
  • Constipation
  • Cramping
There are specific foods that are more likely to cause an intolerance in your body. So if you have the symptoms listed above, you may want to start by looking at the following foods:
  • Cow’s milk
  • Yogurt
  • Ice cream
  • Wheat
  • Onion
  • Garlic
  • High fructose corn syrup
  • Fruit juices & sugary beverages
  • Sweets/Desserts

Now let’s dig into how you can tell the difference between a food intolerance and an allergy.

Food Allergies and Sensitivities

Unlike food intolerances, allergies and sensitivities involve your immune system. As you know, your immune system protects you from things like viruses and bacteria. But it can also go on alert when you eat something your body perceives as an invader.

When your immune system mounts a response to a foreign or dangerous substance, it reacts in a variety of ways. One of those responses is inflammation.

Inflammation gets a bad rap these days. But it actually serves a purpose. Your body inflames as part of a healing or protective response. And this is a good thing. 

But problems arise when inflammation gets out of control or becomes systemic (all over the place for long periods of time). It’s now well-accepted in the medical community that inflammation can negatively affect our health, especially if it becomes chronic. 

When your immune system responds to a food, you may also experience acute symptoms like hives or difficulty breathing.

Food allergies can be serious. Remember the EpiPen I mentioned? If you’ve got one, you know to steer clear of eating the offending food. You probably don’t want to touch it at all. Or in some cases, even be in the same room with it.

When your immune system is reacting to a food, what you are experiencing is either a food allergy or food sensitivity.

What causes food allergies and sensitivities?

Food allergies and sensitivities are triggered when your immune system identifies a specific food protein as an enemy and reacts by producing antibodies to fight it. A common trigger for an immune response to food is a condition known as leaky gut. 

When you have leaky gut, proteins from the foods you eat escape the walls of your intestine and enter the bloodstream uninvited. The immune system mounts a response and creates antibodies specific to that protein. Then in the future when you eat this food, your body recognizes it as an unwanted invader. 

What’s the difference between a food allergy and a sensitivity?

While both involve your immune system, food allergies and sensitivities trigger different immune functions. Generally, food allergies are more severe and occur quickly after you eat the offending food. 

You’ve probably heard more about food allergies than sensitivities. But food sensitivities are actually far more common. Up until fairly recently though, sensitivities have been difficult to pinpoint for a variety of reasons. 

Food sensitivity reactions can be: 

Delayed — A food you are sensitive to won’t always produce an immediate reaction. Sometimes it can be hours or days before you realize you’re reacting to something. This can make it difficult to figure out the offending food.

Dose-dependent — With food sensitivities, how much of the offending food you consume can make a difference. Sometimes a small dose of a food won’t cause a reaction, but a full serving will.

Greatly varied in symptoms — Sensitivities show up as a variety of symptoms that you might not associate with a reaction to something you ate.

Food allergies are easier to identify and diagnose because the reactions are often: 

Immediate — When your body encounters an allergen, the immune system reacts swiftly and efficiently, usually within minutes or even seconds.

Severe — The body can react strongly to an allergen so the reaction is obvious, and sometimes severe enough to be life-threatening.

Easy to recognize — Most people are aware of the common symptoms of an allergic reaction: hives, itching, swelling, dizziness, and anaphylaxis.

Symptoms of food allergies include:
  • Vomiting and diarrhea
  • Hives and itchiness
  • Swelling of the face, lips, tongue
  • Breathing difficulties caused by the swelling of the throat and airways
  • Dizziness, lightheadedness, and fainting
  • Sudden drop in blood pressure
  • Fast, irregular pulse
90% of allergic reactions can be attributed to 8 foods:
  • Milk
  • Eggs
  • Fish
  • Shellfish
  • Peanuts
  • Tree nuts
  • Wheat
  • Soybeans

Food sensitivities have less severe symptoms with delayed onset. So while many people pinpoint their food allergies, sensitivities often go undiagnosed.

Symptoms of food sensitivities include:
  • Headaches
  • Migraines
  • Bloating
  • Abdominal pain
  • Diarrhea
  • Chronic pain like fibromyalgia or joint aches

How do I know if I have food sensitivities?

Honestly, it’s hard to figure out your food sensitivities on your own. You can keep a food and reaction journal. But because sensitivity timing and symptoms can vary so widely, it’s hard to pinpoint sensitivities with this method.

Your best bet is to work with your practitioner and do some food sensitivity testing. But beware. There are a lot of tests on the market that are not particularly effective.

Many of my clients come to me frustrated because their doctors can’t help them figure out what’s making them feel bad. Or worse yet, they’re told that there just isn’t anything wrong. Or it’s all in their head…

But that’s not true. Your symptoms are real. And oftentimes food sensitivities are a pivotal piece of the puzzle. While figuring out which foods you’re sensitive to on your own is difficult, there are ways to accurately test and find out for sure

If you’re ready to dig in and figure it out, click below to schedule a consultation. We can talk about what’s bothering you and formulate a game plan to not only find the problem, but to get you feeling better.

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Alyssa Simpson RD, CDE, CLT
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