What can cause pain and redness in the context of an infection?

Vasodilation and increased blood flow are key physiological responses that occur during an infection and are responsible for the symptoms of pain and redness in the affected area. When the body detects an infection, the immune system responds by releasing chemicals that cause blood vessels to dilate (vasodilation). This process increases blood flow to the site of the infection, which brings immune cells and nutrients to help fight off pathogens.

The additional blood flow also contributes to the characteristic redness (erythema) seen in inflamed tissues, as there is more oxygenated blood reaching the area. Pain can accompany this response due to a combination of increased pressure from the swelling, activation of pain receptors from inflammatory mediators, and the direct action of inflammatory substances released during the immune response.

In contrast, the other options do not directly contribute to pain and redness caused by infection. Reduced oxygen availability can impair healing but does not cause these symptoms directly. A high protein diet and excessive hydration may have other health implications but do not play a role in the immediate inflammatory response associated with infections.