Some individuals develop allergic symptoms without the involvement of IgE. But what exactly is IgE? Let’s take a look.

IgE is a highly reactive antibody that protects us from invasion by parasites. While it’s incredibly helpful in protecting our bodies from parasites, for some individuals it can also recognise harmless foreign materials and initiate ‘protection’ from them. These are “allergens” and include plant pollens, animal dander, food proteins, and so on. For these hypersensitive patients, their IgE pays attention to what it should be ignoring, leading to a rise in allergy symptoms.

Non-IgE allergies can occur when other antibodies react adversely with harmless allergens. This is where it can easily get complicated. To help simplify and understand these varying hypersensitive reactions, they have been classified into four distinct types. These types are used to appreciate the variety of allergic mechanisms which occur in the immune system and can help you better understand your reaction. Please take note that while this is helpful to gain insight into allergic reactions, to fully understand your allergies it is recommended to have a professional assessment.

Four types of hypersensitivity

  • Type 1 hypersensitivity
    • Type 1 hypersensitivity occurs immediately or very soon after contact with an allergen. It is IgE-driven and may include asthma, dermatitis, urticaria, hay fever, sinus trouble and conjunctivitis allergies. This hypersensitivity is responsible for the most fatal and near-fatal reactions from anaphylaxis.

  • Type 2 hypersensitivity
    • Type 2 hypersensitivity is driven by IgG and IgM antibodies. These antibodies bind directly to cell walls and lead to their destruction. In health this is beneficial as it protect our bodies from invading parasites. But, they can also do significant damage. When the antibodies bind to cells in a blood transfusion or donated kidney graft, they can wreak havoc. As well, if they bind to our own issues, they have the ability to produce autoimmune diseases.
  • Type 3 hypersensitivity
    • Type 3 hypersensitivity is driven by IgG and IgM antibodies. The antibodies bind to allergens floating free in the bloodstream. In doing so, it creates an immune complex. If they become too many or if the immune system cannot handle them, they are then dumped into other tissues and cause a great amount of damage. Examples of this reaction are found in rheumatoid arthritis and some forms of allergy involving mould, vegetables, paint and wood.
  • Type 4 hypersensitivity
    • Type 4 hypersensitivity is different from the previous three as it creates unique reactions. The reactions are delayed, meaning the immune cells (not antibodies) react against an allergen over time. For many, this is the underlying mechanism of contact allergy in skin.

It is important to remember that reactions can vary greatly between patients. If you are having an allergic reaction of any hypersensitivity level, please contact an allergy specialist.