An antigen and allergen both cause your immune system to respond. An allergen is an antigen, but not all antigens are allergens.
An antigen is any substance that’s capable of causing your immune system to produce antibodies. They are typically organic, or living, produced proteins. An allergen is any antigen that causes an allergic reaction.
These foreign invaders are usually harmful and trigger your immune system to fight them.
An allergen is an environmentally produced substance that causes an allergic reaction, although the substance may not be harmful. Allergens cause no reaction in some, yet a hypersensitive one in others. Couple common allergens include:
- dust mites
- toxic mold
- food, drugs
- animal dander
- insect bites, stings
In some cases, an antigen may evolve and change its protein composition. This change can cause your previous antibody driven immunity less effective or completely ineffective. Thus, virus infection recurrence may occur, i.e. common cold or influenza.