Arginase has a rich history in cutaneous biology and pathophysiology, as discussed in this blog on August 1, 2102. It is a topic, like a cicada, that raises its head annually. Its role in wound healing was further investigated by Campbell et al (2013). Arginase was deleted in alternatively activated macrophages, and this enzyme, which increases several-fold during wound healing in the mouse, was abrogated. Arginase usually peaks five days after an excisional wound; in the arginase knockout there was increased inflammation and slowed healing. Chemical inhibitors of arginase mimicked the effects seen in the knockout mouse. Arginase modulation might be therapeutically useful in wounds with abnormal healing (e.g., keloids or hypertrophic scars) and in wounds with decreased healing, as occurs commonly in diabetes, aging, vascular diseases. Like other physiological pathways — following the Goldilocks principle may be important, you need just the right amount: not too much and not too little.