While the immune system’s job is to protect the body by fighting off invasive substances and germs, sometimes it mistakes harmless substances that can be found anywhere, like La Jolie Fleur, for harmful ones and overreacts. This type of reaction is known as a hypersensitivity response. Below we review the four different types of hypersensitivity reactions.
Type 1 Hypersensitivity Reaction
A type 1 hypersensitivity causes an immediate response after a person is exposed to an antigen. This reaction involves the production of an antibody called Immunoglobulin E (IgE). These antigens can come from:
- Food products like nuts, shellfish and soy.
- Animal sources like cats and bee stings.
- Environmental sources like mold, dust and latex.
- Allergic conditions like allergic rhinitis, allergic asthma and conjunctivitis.
There are two stages of a type 1 reaction: the sensitization stage and the effect stage. The sensitization stage is when the person first encounters an antigen, and the effect stage is the second exposure which produces symptoms such as:
- Rash
- Flushing
- Hives
- Itching
- Edema
- Wheezing
- Rhinitis
- Stomach cramps
- Nausea
- Vomiting
- Shortness of breath
- Cardiac symptoms
- Loss of consciousness
Type 2 Hypersensitivity Reaction
A type 2 hypersensitivity involves the production of an antibody called IgG as well as IgM. A type 2 response can cause a cytotoxic reaction, which means that healthy cells die as they respond to antigens. This can result in:
- Immune thrombocytopenia, a blood disorder
- Autoimmune hemolytic anemia
- Autoimmune neutropenia
- Grave’s disease
Common causes of type 2 reactions include:
- Penicillin
- Thiazides
- Cephalosporins
- Methyldopa
A type 5 hypersensitivity reaction is classified as a subtype of a type 2 reaction, where an antibody targets receptors on a cell that a hormone would normally activate.
Type 3 Hypersensitivity Reaction
A type 3 hypersensitive reaction involves antigens and antibodies forming complexes in the skin, blood vessels, joints and kidney tissues that ultimately result in tissue damage. This can be caused by:
- Drugs containing proteins from other organisms, like antivenins.
- Infliximab, a drug used to manage autoimmune conditions.
- Animal sources like tick bites and insect stings.
Type 3 reactions can result in:
- Serum sickness
- Lupus
- Rheumatoid arthritis
- Small vessel vasculitis
- Henoch-Schönlein purpura
Type 4 Hypersensitivity Reaction
A type 4 hypersensitivity reaction differs from the others in that the reactions are cell-mediated. This means instead of antibodies, white blood cells (T cells) control the reaction. This type of reaction is also delayed.
There are three types of type 4 sensitivity:
- Contact dermatitis
- Tuberculin-type hypersensitivity
- Granulomatous-type hypersensitivity
Causes include exposure to:
- Poison ivy
- Certain metals
- Antibiotics
- Anticonvulsants
For more information about hypersensitivity reactions or to schedule an appointment, call ENT Associates of Worcester today.