## Core Concept
Skin grafting involves transplanting a portion of skin from one area of the body to another or from a donor. For the graft to take, the recipient site must be free of infection, as bacteria can destroy the graft. Certain infections make skin grafting risky or contraindicated.

## Why the Correct Answer is Right
The correct answer, **C. Herpes simplex**, indicates that active herpes simplex infection is a contraindication for skin grafting. This is because herpes simplex virus can infect the graft site, leading to viral dissemination or delaying graft take. The virus can also cause local tissue destruction, making it difficult for the graft to adhere and integrate.

## Why Each Wrong Option is Incorrect
* **Option A:** Impetigo is a superficial skin infection caused by Staphylococcus aureus or Streptococcus pyogenes. While active infection is typically a contraindication for skin grafting, impetigo can often be treated and cleared before grafting.
* **Option B:** Eczema or atopic dermatitis is a chronic inflammatory skin condition. Though it's a skin condition, it's not an absolute contraindication for skin grafting unless there's an active flare or significant disruption of the skin barrier.
* **Option D:** Psoriasis is a chronic autoimmune skin condition characterized by rapid skin cell growth. While it's a skin condition, it's not typically considered a contraindication for skin grafting.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **active infections**, particularly those caused by viruses like herpes simplex, are significant contraindications for skin grafting due to the risk of graft failure or viral dissemination. Always consider the status of the recipient site before performing a skin graft.

## Correct Answer: C. Herpes simplex.