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:
Table of Contents
What are allergies?
Allergies are a type of hypersensitivity reactions mediated by immunoglobulin E (IgE). Allergies are not related to any diseases or infections. These 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 Disease | Tissue Affected |
| Multiple Sclerosis | Myelin on axons in the CNS |
| Aplastic anemia | Bone marrow |
| Rheumatoid arthritis | Joints |
| Type I diabetes | Beta islets cells of the pancreas |
| Crohn’s disease | Gastrointestinal tract infection |
| Ulcerative colitis | Large intestine |
| Celiac disease | Tiny intestinal microvilli in cross-reaction with gluten |
| Grave’s disease | Thyroid gland (hyperthyroidism) |
| Hashimoto’s disease | Thyroid gland (hypothyroidism) |
| Psoriasis | Skin |
| Myasthenia gravis | Skeletal muscles |
| Lupus | Many tissues |
| Addison’s disease | Adrenal 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 between allergies and autoimmunity
| SN | Allergies | Autoimmune Disease |
| 1 | In 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. |
| 2 | External 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. |
| 3 | Allergies are often equated with type I hypersensitivity reactions. | Most autoimmune diseases are linked to type III or type II hypersensitivity reactions. |
| 4 | Mast cells and IgE antibodies play a central role in the allergic response | T and B cells are the primary factors in autoimmunity. |
| 5 | The 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. |
| 6 | Some 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
- byjus.com/biology/allergies-autoimmunity/
- August et. al. Autoimmunity and Allergy: Session 7 https://www.ibiology.org/sessions/session-7-autoimmunity-and-allergy/
- https://centrespringmd.com/do-allergies-trigger-autoimmune-disease/