When the immune system makes a mistake and attacks own cells it produces an allergic reaction?

This statement is not entirely accurate. An allergic reaction is a response to a foreign substance (an allergen) that the immune system perceives as harmful. When the body comes into contact with an allergen, the immune system produces antibodies to fight it off. These antibodies bind to the allergen and cause the release of histamine and other chemicals, which lead to allergy symptoms such as sneezing, a runny nose, watery eyes, and itching.

In the case of autoimmune diseases, the immune system mistakenly attacks the body's own tissues. This can lead to inflammation and damage to various organs and tissues. Autoimmune diseases include conditions such as rheumatoid arthritis, lupus, and multiple sclerosis.

Therefore, allergic reactions and autoimmune diseases are distinct responses of the immune system. While both involve immune responses, they differ in the target of the immune attack (foreign substances vs. self-tissues) and the resulting symptoms and conditions.