**Core Concept**
Hand and foot syndrome, also known as palmar-plantar erythrodysesthesia, is a type of skin toxicity associated with certain chemotherapeutic agents. It is characterized by redness, swelling, and peeling of the skin on the hands and feet.

**Why the Correct Answer is Right**
Hand and foot syndrome is primarily caused by the extravasation of chemotherapeutic agents, such as fluoropyrimidines (5-FU), capecitabine, and doxorubicin, into the skin. This leads to damage to the rapidly dividing cells in the skin, resulting in the characteristic symptoms. The exact mechanism is thought to involve the inhibition of thymidylate synthase, which is essential for DNA synthesis and repair in rapidly dividing cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while certain antibiotics can cause skin toxicity, they are not the primary cause of hand and foot syndrome.
**Option B:** This option is incorrect because while certain immunotherapies can cause skin reactions, they are not typically associated with hand and foot syndrome.
**Option C:** This option is incorrect because while certain targeted therapies can cause skin toxicity, they are not the primary cause of hand and foot syndrome.

**Clinical Pearl / High-Yield Fact**
Hand and foot syndrome is a dose-dependent adverse effect of certain chemotherapeutic agents, and its severity can be reduced by using prophylactic measures such as topical creams and dose adjustments.

**Correct Answer: C. Doxorubicin**