Hypersensitivity reactions

Hypersensitivity reactions are exaggerated immune responses to substances that are usually harmless, such as pollen, pet dander, or certain foods. There are four main types: Type I (allergies), where the body releases chemicals like histamine; Type II involves antibodies targeting specific cells; Type III is triggered by immune complexes; and Type IV is a delayed response that can take hours or days. These reactions can cause symptoms ranging from mild (like sneezing or rashes) to severe (like anaphylaxis), highlighting how the immune system can sometimes overreact to non-threatening triggers.