An __________ is a response to a normally harmless substance.

An allergy is an immune response that occurs when the body mistakenly identifies a normally harmless substance, such as pollen, pet dander, or certain foods, as a threat. This immune reaction can lead to a variety of symptoms, including itching, swelling, and difficulty breathing, depending on the severity of the allergy. The body's immune system produces antibodies, specifically Immunoglobulin E (IgE), in response to the allergen, leading to the release of histamines and other chemicals that result in allergic symptoms. Understanding the concept of allergies is important in the field of cosmetology since some clients may have allergies to specific ingredients found in beauty products or treatments, which can impact their safety and comfort during services.