What is an over reaction in the immune system?
An allergic reaction; especially one that results in anaphylactic shock.
An allergic reaction is the body's way of responding to an "invader." When the body senses a foreign substance, called an antigen, the immune system is triggered. The immune system normally protects the body from harmful agents such as bacteria and toxins. Its overreaction to a harmless substance (an allergen) is called a hypersensitivity reaction, or an allergic, reaction.
Genes determine whether you would inherit diabetes or not. Diabetes is dependent on the immune system. The immune system is in turn dependent on genes. If there is any imbalance in the immune system, it triggers an autoimmune reaction. Other factors like gender, diet and body reaction also play a role in determining if you would inherit diabetes or not.
The immune system views the allergen as a foreign substance and starts producing antibodies to prevent the allergen from doing damage to the body. The immune systems response to the allergen is what is called the allergic reaction. Without the reaction, the person wouldn't get sick. So it is actually the immune systems response to the foreign body that makes the person sick.