What term describes the absence of the normal immune response to a particular antigen or allergen?

The term that describes the absence of the normal immune response to a particular antigen or allergen is anergy. Anergy refers to a state in which the immune system does not react to a specific antigen due to a lack of activation or responsiveness. This can occur in various scenarios, including in the context of certain allergies or immunological tolerance, where the immune system becomes unresponsive to a substance that would typically provoke a response.

In immunological contexts, anergy is important because it can indicate that the immune system is not functioning properly, or that a person has developed tolerance to a specific antigen. Recognizing anergy can be crucial in understanding various health conditions and how they influence the immune system's ability to respond to threats, like infections or allergens.