Your immune system protects you from diseases, viruses and infections. However, sometimes it mistakes a harmless substance, like pollen at The Philadelphia Flower Market for a dangerous intruder and overreacts. This type of response is known as a hypersensitive reaction, of which there are four. We review how to recognize the four types of hypersensitive reactions below.
Type 1
A type 1 hypersensitive reaction causes an immediate response following exposure to an antigen and involves the production of the antibody Immunoglobulin E.
Type 1 reactions take place in two stages: the sensitization stage, when the antigen is first encountered, and the effect stage, when symptoms present. Symptoms of a type 1 reaction include:
- Rash
- Flushing
- Hives
- Itching
- Edema
- Wheezing
- Rhinitis
- Stomach cramps
- Nausea
- Vomiting
- Shortness of breath
- Cardiac symptoms
- Loss of consciousness
This type of reaction can be triggered by:
- 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.
Type 2
A type 2 reaction involves the production of the antibodies Immunoglobulin G and Immunoglobulin M. This type of reaction can by cytotoxic, 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
Type 2 reactions can be caused by:
- Penicillin
- Thiazides
- Cephalosporins
- Methyldopa
There is a subtype of type 2 reactions, known as a type 5 reaction. This type of reaction occurs when an antibody targets receptors on a cell that a hormone would normally activate.
Type 3
A type 3 reaction entails antigens and antibodies forming complexes in the skin, blood vessels, joints and kidney tissues. This ultimately can result in tissue damage as well as:
- Serum sickness.
- Rheumatoid arthritis.
- Small vessel vasculitis.
- Henoch-Schönlein purpura.
Type 3 reactions may 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 4
A type 4 hypersensitive reaction differs from the others in that the reactions are cell-mediated, meaning white blood cells known as T cells control the reaction rather than antibodies. This type of reaction also differs in that it is a delayed reaction rather than immediate.
The three ways a type 4 reaction can present are:
- Contact dermatitis
- Tuberculin-type hypersensitivity
- Granulomatous-type hypersensitivity
These can be caused by:
- Poison ivy
- Certain metals
- Antibiotics
- Anticonvulsants
For more information or to schedule an appointment for an allergy test, call Pinnacle ENT Associates today.