Final answer:
Acute effects occur rapidly after exposure to a substance, delayed effects take one to two days to manifest after secondary exposure to an antigen, and allergic reactions vary in severity depending on the type and scale of the body's response to allergens.
Step-by-step explanation:
The differences between acute, delayed, and allergic effects involve the timing and the mechanisms by which these reactions occur. Acute effects are immediate, typically caused by a rapid onslaught of symptoms following exposure to a pathogen or contaminant, as exemplified by influenza which exhibits symptoms within hours or days. In contrast, delayed effects occur over a longer period, often 24-72 hours following a secondary exposure, and are championed by a T-cell mediated response that involves cytokines and leads to symptoms like contact dermatitis. Allergic reactions are caused by hypersensitivity to certain antigens, ranging from mild effects treated with antihistamines to severe, life-threatening anaphylaxis. Type I hypersensitivity reactions are immediate, involving mast cells and the release of histamines, whereas late-phase type I reactions enlist eosinophils and other inflammatory cells, causing symptoms many hours after the initial exposure.