What is the Difference Between Intolerance and Allergy

Intolerance and allergy can be both triggered by certain foods and drugs. However, they are two different biological reactions or conditions that occur in the human body. The digestive system is mostly involved in cases of intolerance, while the immune system is involved in allergies. Therefore, intolerance and allergy should be managed differently.

The key difference between intolerance and allergy is their underlying mechanisms. Intolerance is a condition where the gut is sensitive to certain foods or unable to handle adverse effects from certain drugs. Allergies, on the other hand, occur when the immune system overreacts to substances such as dust, mites, pets, pollen, food, insects, ticks, and drugs.

CONTENTS

1. Overview and Key Difference
2. What is Intolerance 
3. What is Allergy
4. Similarities – Intolerance and Allergy
5. Intolerance vs Allergy in Tabular Form
6. Summary – Intolerance vs Allergy
7. FAQ – Intolerance and Allergy

What is Intolerance?

Intolerance is a condition where the gut is sensitive to certain foods. When people have a food intolerance, they have difficulty digesting certain foods. Drug intolerance refers to the inability to tolerate the adverse effects of certain medications. Drug intolerance is influenced by how the body metabolizes medications and can also vary due to genetic differences among individuals.

Symptoms of food intolerance include diarrhea, bloating, flatulence, and stomach pain. On the other hand, symptoms of drug intolerance include hives, skin rash, swelling, wheezing, liver toxicity, and bleeding.

Figure 01: Lactose Intolerance

Intolerance can be diagnosed through physical examination, blood tests, and skin biopsy. Furthermore, treatment options for intolerance include changing the diet and limiting or eliminating problematic food, taking antidiarrheal medications, and stopping the drug that causes adverse reactions.

What is Allergy?

Allergy is caused by the immune system overreacting to certain substances in the environment that are generally harmless to most people. These substances include foods, inhalants, medications, latex, venoms, or insect bites. The symptoms of an allergic reaction can include a runny nose or sneezing, pain or tenderness around the cheeks, eyes, or forehead, coughing, wheezing or breathlessness, itchy skin, hives, diarrhea, feeling of sickens, swollen eyes, lips, mouth or throat.

Figure 02: Allergy

An allergy can be diagnosed through physical examination, skin prick, and blood test. Furthermore, allergies can be treated by avoiding allergens, taking antihistamines and asthma medications, using nasal sprays, decongestants, and immunotherapy.

Similarities Between Intolerance and Allergy

1. Intolerance and allergy can be triggered by foods and drugs.
2. Both may cause similar symptoms, such as skin rashes, swelling, and diarrhea.
3. Both can be diagnosed through physical examination and blood tests.
4. They can be treated by avoiding triggers and specific medications.

Difference Between Intolerance and Allergy

Definition

1. Intolerance is a wide range of adverse reactions to foods due to a sensitive gut or an inability to tolerate the adverse effects of certain medications.
2. Allergy is an immunologic reaction of the body in order to respond to an allergen.

Severity

1. Intolerance is a less severe condition.
2. Allergy is a more severe condition.

System Involved

1. Intolerance mainly involves the digestive system.
2. Allergy mainly involves the immune system.

Causes

1. Intolerance can be caused by a lack of an enzyme needed to digest certain foods or genetic variation among the population to tolerate the adverse effects of certain drugs.
2. Allergy can be caused by genetic changes and the environment.

Symptoms

1. The symptoms of food intolerance include nausea, stomach pain, gas, vomiting, heartburn, constipation, headaches, skin rash, and hives, while the symptoms of drug intolerance include rashes, gastrointestinal problems, headaches, coughing, muscle aches, and fevers.
2. The symptoms of allergy include a runny nose, rash, itching, redness, swelling bumps, flaky skin, and cracked skin.

Diagnosis

1. Diagnosis of intolerance is through health history, physical examination, hydrogen breath test, skin biopsy, and genetic test.
2. Diagnosis of allergy is done through physical examination, skin test, and blood test.

Treatment

1. The treatments for intolerance include changing the diet to limit or eliminate problem foods, taking over-the-counter medicines like antacids or antidiarrheals, and avoiding drugs that result in adverse reactions in the body.
2. The treatments for allergy include taking steroids, antihistamines, allergy shots (subcutaneous immunotherapy (SCIT), and sublingual immunotherapy (SLIT).

The following table summarizes the difference between intolerance and allergy.

Summary – Intolerance vs Allergy

Intolerance and allergy are two conditions that can be triggered by certain foods and drugs. They may cause similar symptoms, such as skin rashes, hives, diarrhea, swelling, etc. However, they are different. Intolerance is a condition where people have difficulty digesting certain foods and have an unpleasant physical reaction when they eat certain foods due to a sensitive gut or an inability to tolerate the adverse effects of a medication. On the other hand, allergy is a condition where the immune system of people overreacts to certain substances in the environment that are harmless to most people. This is the key difference between intolerance and allergy.

FAQ: Intolerance and Allergy

1. How do I know people have a food intolerance?

• Food intolerances occur when the body has trouble digesting a certain food, such as milk, wheat, rye, and barley. The symptoms are mostly digestive in nature and include stomachache, diarrhea, nausea, vomiting, gas, and bloating. Some people also report headaches and fatigue.

2. How to fix food intolerance?

• Food intolerances tend to be lifelong. Most people can relieve symptoms if they reduce or limit foods that cause digestive problems. The other treatments include taking over-the-counter medicines like antacids or antidiarrheals.

3. What is causing allergies?

• The common allergy triggers include pollen, animal dander, dust mites, mold, certain foods like peanuts, tree nuts, wheat, soy, fish, shellfish, eggs and milk, venom, insect stings, such as from a bee or wasp, and medicines such penicillin or penicillin-based antibiotics.

4. What are the main allergy symptoms?

• Some of the main symptoms of an allergic reaction include itchy, watery eyes, itchy nose, sneezing, runny nose, rashes, hives, stomach cramps, vomiting, diarrhea, bloating swelling, redness, pain, cough, throat closing, wheezing, chest tightness, light-headedness and a sense of impending doom.

5. How can allergies be treated?

• Allergies can be managed by avoiding triggers, using antihistamines to block histamine (which causes allergic swelling), and undergoing immunotherapy, such as allergy shots (subcutaneous immunotherapy or SCIT) and sublingual immunotherapy (SLIT).

 Reference:

1. “Allergy Symptoms: Signs, Symptoms, and Treatment.” WebMD.
2. “Food Intolerance: Symptoms, Causes and Treatment Options.” Cleveland Clinic.

Image Courtesy:

1. “Worldwide prevalence of lactose intolerance in recent populations” By NmiPortal – Own work / Food Intolerance Network (CC BY-SA 3.0) via Commons Wikimedia
2. “Cold allergy symptoms” By Bangerth – Own work (CC BY-SA 3.0) via Commons Wikimedia

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