The key difference between type I and type IV hypersensitivity is that type I hypersensitivity is an immediate hypersensitivity that occurs within 24 hours after exposure to allergens, while type IV hypersensitivity is a delayed hypersensitivity that occurs 48–72 hours after exposure to the allergen.
A hypersensitivity reaction occurs when the immune system mistakenly identifies harmless substances as harmful. Therefore, it is an extreme or unnecessary immune response that the body generates to antigens. There are several types of hypersensitivity reactions, such as types I, II, III, and IV.
CONTENTS
1. Overview and Key Difference
2. What is Type I Hypersensitivity
3. What is Type IV Hypersensitivity
4. Similarities – Type I and Type IV Hypersensitivity
5. Type I vs. Type IV Hypersensitivity in Tabular Form
6. FAQ – Type I and Type IV Hypersensitivity
7. Summary – Type I vs. Type IV Hypersensitivity
What is Type I Hypersensitivity?
Type I hypersensitivity is a hypersensitivity reaction that causes an immediate response, and it happens within 24 hours after a person has been exposed to an antigen. In type I hypersensitivity reaction, the body specifically responds to an antigen by producing a type of antibody called IgE. Type I hypersensitivity can be caused by allergens that come from food products such as nuts, shellfish, soy, and animal sources such as cats, rats, or bee stings, environmental sources such as molds, latex, and dust, and allergic conditions like allergic rhinitis, allergic asthma, and conjunctivitis. Moreover, signs and symptoms of type I hypersensitivity reaction include rash, flushing, hives, itching, edema, wheezing, rhinitis, stomach cramps, nausea and vomiting, shortness of breath, cardiac symptoms, and loss of consciousness.
Figure 01: Type I Hypersensitivity
Type I hypersensitivity can be diagnosed through physical symptoms evaluation and blood tests. Furthermore, type I hypersensitivity can be treated through adrenaline or epinephrine, systemic glucocorticoids, and antihistamines.
What is Type IV Hypersensitivity?
Type IV hypersensitivity is a delayed hypersensitivity reaction. Unlike other types of hypersensitivity reactions, this type is not antibody-mediated. Instead, type IV hypersensitivity is cell-mediated. White blood cells in the human body, called T cells, usually control type IV hypersensitivity. Type IV hypersensitivity is further classified into type 4a, type 4b, type 4c, and type 4d based on the type of T cell that is involved and the reaction these cells produce in the body. The common causes of type 4 hypersensitivity reactions are exposure to poison ivy, certain metals, and drugs such as antibiotics or anticonvulsants. Moreover, signs and symptoms of type 4 hypersensitivity may include fever, malaise, pruritus, erythema urticarial, perioral paresthesia, angioedema, wheezing, and multiorgan problems.
Figure 02: Hypersensitivity
Type IV hypersensitivity can be diagnosed through skin biopsy, patch test, X-ray, lymph node biopsy, enzyme analysis, and salivary gland analysis. Furthermore, treatment options for type IV hypersensitivity may include giving topical steroid medications such as rifampin, isoniazid, pyrazinamide, ethambutol, and steroid therapy (methotrexate).
What are the Similarities Between Type I and Type IV Hypersensitivity?
- Type I and type IV hypersensitivity are two different types of hypersensitivity reactions.
- Both types are unnecessary immunological reactions to harmless allergens.
- Both types can cause similar symptoms such as rash, fever, etc.
- They can be diagnosed through physical symptoms evaluation.
- They are mainly treated through specific medications.
What is the Difference Between Type I and Type IV Hypersensitivity?
Type I hypersensitivity is an immediate hypersensitivity that occurs within 24 hours after exposure to the allergens, while IV hypersensitivity is a delayed hypersensitivity that occurs 48–72 hours after exposure to the allergen. Thus, this is the key difference between type I and type IV hypersensitivity. Furthermore, type I hypersensitivity is mediated by antibodies such as IgE. On the other hand, type IV hypersensitivity is mediated by white blood cells such as T cells.
The infographic below presents the differences between type I and type IV hypersensitivity in tabular form for side-by-side comparison.
FAQ: Type I and Type IV Hypersensitivity
What are examples of type IV hypersensitivity?
Contact dermatitis and drug hypersensitivity are examples of type IV hypersensitivity.
What are examples of type 1 hypersensitivity?
Asthma, rhinitis, conjunctivitis, and dermatitis are examples of type I hypersensitivity.
Why is type 1 hypersensitivity immediate?
Type 1 hypersensitivity is immediate because it occurs within 24 hours of exposure to the allergen or antigen.
Summary – Type I vs. Type IV Hypersensitivity
Hypersensitivity reactions are exaggerated immunological responses occurring in response to antigens or allergens. There are different hypersensitivity reactions, such as type I, II, III, and IV hypersensitivity reactions. Type I hypersensitivity is an immediate hypersensitivity that occurs within 24 hours after exposure to allergens, while IV hypersensitivity is a delayed hypersensitivity that occurs 48–72 hours after exposure to the allergen. So, this summarizes the difference between I and type IV hypersensitivity.
Reference:
1. H;, Abbas M;Moussa M;Akel. “Type I Hypersensitivity Reaction.” National Center for Biotechnology Information, U.S. National Library of Medicine.
2. “Type IV Hypersensitivity.” An Overview | ScienceDirect.
Image Courtesy:
1. “2228 Immune Hypersensitivity new (cropped)” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
2. “2228 Immune Hypersensitivity new” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia