Which of the following is a common symptom of an allergic reaction?

Redness and swelling are hallmark symptoms of an allergic reaction. This occurs as the body's immune system responds to an allergen, releasing chemicals such as histamines that lead to inflammation. The reaction causes blood vessels to dilate and become more permeable, resulting in the visible signs of redness and the accumulation of fluid in affected tissues, leading to swelling. These symptoms can manifest in various forms on the skin, such as rashes, hives, or even more severe conditions depending on the individual and the allergen involved.

In contrast, increased hydration, improved texture, and enhanced shine do not reflect the physiological responses associated with allergic reactions. These conditions relate more to cosmetic improvements or skin health rather than the adverse effects of an allergy.