**Core Concept**
Formication is a tactile hallucination characterized by a sensation of insects crawling under the skin. This phenomenon is often associated with various underlying conditions, including substance use disorders, neuropathic pain, and psychiatric illnesses.

**Why the Correct Answer is Right**
Formication is typically triggered by the release of certain neurotransmitters, such as dopamine and serotonin, which can alter the perception of sensory stimuli. In the context of substance use disorders, formication is often a symptom of withdrawal or intoxication. For instance, in cocaine users, formication is thought to result from the blockade of dopamine reuptake, leading to an overabundance of dopamine in the synaptic cleft. This can cause individuals to perceive sensations of crawling or creeping under the skin.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specifically describe a condition associated with hallucinations of worms crawling over the body. While certain psychiatric conditions may present with hallucinations, they are not typically characterized by the specific symptom of formication.
**Option B:** This option is incorrect because it refers to a different type of hallucination altogether. Visual hallucinations, such as those experienced by individuals with schizophrenia, involve the perception of visual stimuli that are not present in the environment.
**Option C:** This option is incorrect because it describes a different type of sensory disturbance altogether. Dysesthesia refers to a condition characterized by an abnormal sensation of pain or discomfort in response to a stimulus that would not normally be painful.

**Clinical Pearl / High-Yield Fact**
The term "formication" is derived from the Latin word "formica," meaning "ant," which highlights the characteristic sensation of insects crawling under the skin. This symptom is often associated with substance use disorders and can be a key diagnostic clue in the evaluation of patients presenting with unusual sensory disturbances.

**Correct Answer:** C. Ekbom syndrome, also known as formication, is a condition characterized by the sensation of insects crawling under the skin.