What symptom might be observed with a deficiency of Wei Qi?

A deficiency of Wei Qi, which is often referred to as "defensive Qi," plays a crucial role in protecting the body against external pathogens and maintaining overall health. When Wei Qi is deficient, the body becomes less capable of warding off illnesses, leading to an increased susceptibility to infections, particularly from external sources. This manifests as frequent colds, flus, or other infections that can invade the body more easily due to the compromised immune system.

The other options do not directly relate to the deficiency of Wei Qi. A warm sensation in the stomach is typically associated with excess heat conditions or digestive issues rather than Wei Qi deficiency. Dark and dry skin usually points to issues related to blood deficiency or dryness constitution rather than an insufficient Wei Qi. Severe headaches may indicate various internal disharmonies or excess conditions rather than a straightforward deficiency of Wei Qi.

Thus, frequent external infections serve as the most direct symptom indicative of a deficiency in Wei Qi, highlighting its essential role in maintaining the body's defenses.