What is a common sign of an allergic reaction during a service?

A common sign of an allergic reaction during a service is redness or swelling at the application site. This response occurs because the body is reacting to a substance it recognizes as foreign, leading to inflammation as part of the immune response. When a client experiences an allergic reaction, the localized area might become red, swollen, and sometimes even itchy or painful, indicating that the body is attempting to combat the perceived threat.

In contrast, dryness of the scalp, increased hair shedding, and changes in hair texture may occur due to other factors, such as product use, environmental influences, or underlying hair and scalp health issues, rather than being clear indicators of an allergic reaction. These conditions do not typically involve the same immediate immune response that manifests as redness or swelling, which is why they are not recognized as common signs of an allergic reaction in a professional setting.