Type IV
Type IV reactions take time to occur. During the first exposure to an antigen you touch or inhale, the antigen triggers the production of memory T cells that can recognize it quickly in the future. Subsequent exposures cause a rapid and vigorous immune response.
Macrophages released during this reaction destroy cells of the body that host this foreign antigen or have become infected. Some type IV reactions cause cytotoxic T cells to induce apoptosis in cells hosting identified foreign antigens.
Examples of type IV reactions include [6]:
- Chronic asthma
- Allergic reactions to latex
- Tuberculin reaction
- Transplant tissue rejection
- Contact dermatitis caused by poison ivy
Conclusion
Many things can cause allergic reactions. The specific type of reaction you have depends on several factors, including the allergen responsible. If you have a severe allergic reaction, you should see a doctor immediately to avoid life-threatening complications.
References
[1] http://www.microbiologybook.org/ghaffar/hyper00.htm
[2] https://www.medicinenet.com/what_are_the_four_types_of_allergic_reactions/article.htm
[3] https://www.karger.com/Article/Abstract/154811
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3914752/
[5] http://www.microbiologybook.org/ghaffar/hyper00.htm
[6] http://www.microbiologybook.org/ghaffar/hyper00.htm