GSTM1 and Erythema: These are sub-characterised into blood flow (DermaLab erythema, Full-field Laser Perfusion Imaging, SIAoscopy Hb and optical coherence tomography (OCT) blood flow), skin barrier function (DermaLab TEWL and hydration), tissue morphology (SIAoscopy collagen, OCT attenuation compensation) and pigmentation (Dermalab melanin and SIAoscopy melanin).