Allergies and Autoimmunity: Similarities and Differences

Allergies and autoimmunity are conditions related to the immune system. They occur when antigens activate immune cells.

Allergies and autoimmune diseases follow a similar developmental way, though their presentation is often quite different. Allergic reactions occur when the immune system reacts to foreign environmental substances. With allergies, the invaders are otherwise harmless environmental triggers. On the other hand, autoimmunity is a system of responses from the immune system against the body’s healthy cells and tissues. With an autoimmune disease, our immune system mistakenly identifies the host’s cells for destruction. The brief descriptions of allergies and autoimmune diseases, their similarities and differences are given below:

What are allergies?

Allergies are a type of hypersensitivity reactions mediated by immunoglobulin E (IgE). Allergies are not related to any diseases or infections. Allergies can be observed in various body parts; the effect is mainly seen on the skin and mucus membrane. The immune system recognizes innocuous non-self antigens (e.g., proteins in peanuts) and responds against them. The human body may be sensitive to such specific particles found in the environment. Such particles are called allergens. Allergens are the antigens producing abnormally exaggerated immune responses.

Common allergens are dust, pollen, feathers, latex, pet dander, mites, and even food particles, like peanuts. 

When the body encounters an allergen, antibodies called immunoglobulin E (IgE) are produced in its response. It is followed by the release of chemicals such as histamine and serotonin.

Sneezing, coughing, running nose, red eyes, itchy rashes, or difficulty breathing and swallowing can be allergy symptoms. Allergy to at least one allergen is common throughout the world. However, in recent times more people are prone to allergies due to modern and unhealthy lifestyles, as they have low immunity and high environmental sensitivity.

What are Autoimmunities?

The system of immune responses of an organism against its healthy cells and tissues is autoimmunity. Diseases that occur because of such reactions are called autoimmune diseases. In autoimmunity, the immune system attacks cells expressing self-antigens. Such self-reactive immune cells produce autoantibodies. Thus, autoimmunity is an overburdened immune system causing systemic inflammation.

The higher classes of vertebrates can recognize foreign antigens. Their immune system can distinguish perfectly between their cells and foreign organisms. But, sometimes, the body attacks its cells and tissues due to genetic defects, environmental factors, or some other unknown cause. This results in autoimmune diseases. An imbalance in T cell function (which produces and suppresses the immune response) helps to develop autoimmune diseases.

Rheumatoid arthritis (RA), Graves’ disease, and polymyositis are common examples of autoimmune diseases.

In some cases, allergies trigger autoimmune diseases. One of the examples is the gluten-thyroid connection, where antibodies against it attack thyroid tissue.

Common Autoimmune DiseaseTissue Affected
Multiple SclerosisMyelin on axons in the CNS
Aplastic anemiaBone marrow
Rheumatoid arthritisJoints
Type I diabetesBeta islets cells of the pancreas
Crohn’s diseaseGastrointestinal tract infection
Ulcerative colitisLarge intestine
Celiac diseaseTiny intestinal microvilli in cross-reaction with gluten
Grave’s diseaseThyroid gland (hyperthyroidism)
Hashimoto’s diseaseThyroid gland (hypothyroidism)
PsoriasisSkin
Myasthenia gravisSkeletal muscles
LupusMany tissues
Addison’s diseaseAdrenal cortex

Similarities

  • Both of them have symptoms of general fatigue and sickness.
  • Itching can be a common symptom of both.
  • In the higher immune response, allergy and autoimmune disease result in some redness or swelling.
  • Hypersensitivity can cause both allergies and autoimmunity.

Differences

SNAllergiesAutoimmune Disease
1In allergies, the host immune system reacts abnormally in response to a foreign substance (i.e., an allergen).In autoimmune disease, the host immune system mistakenly attacks healthy tissues and cells of the body.
2External factors, mainly environmental substances like pollen, dust, insect venoms, or food and drugs, trigger the allergies.Internal factors trigger autoimmune diseases, which affect the body’s cells.
3Allergies are often equated with type I hypersensitivity reactions.Most autoimmune diseases are linked to type III or type II hypersensitivity reactions.
4Mast cells and IgE antibodies play a central role in the allergic responseT and B cells are the primary factors in autoimmunity.
5The most common treatments are bronchodilators, corticosteroids, and antihistamines.The most common treatments are immunosuppressants, anti-inflammatory drugs, vitamin D, and omega 3. Sometimes, pain relief medicines and even surgery are required.
6Some examples of allergies are asthma, itchy sensation, redness, watery eyes, etc.Some autoimmune diseases include rheumatoid arthritis, type I diabetes, inflammatory bowel disease, multiple sclerosis, etc.

References

Srijana Khanal

Hello, I am Srijana Khanal. Former faculty teacher in Microbiology Department at National College, NIST. Involved in the field of teaching for almost 10 years. I am very passionate about writing (academic as well as creative). My areas of interest are basic science, immunology, genetics, and research methodology.

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