In addition to the negative effects on the skin barrier, IL-24 was reported to trigger keratinocytes to secrete IL-8, PGE2, and MMP-1 inflammatory mediators [21], and genetic deficiency in IL-24 was shown to partially prevent mice from developing allergic contact dermatitis after exposure to paraphenylenediamine [34], implying that IL-24 contributes to skin inflammatory responses. The gene discussed is MMP1; the disease is allergic contact dermatitis.