Red blood cell
The pathogenesis of erythema ab igne remains unknown. It has been proposed that thermal radiation exposure can induce damage to superficial blood vessels that subsequently leads to epidermal vascular dilation. The dilation of vessels presents morphologically as the initially observed erythema. Red blood cell extravasion and deposition of hemosiderin that follows clinically appears as hyperpigmentation, which can occur in a reticular distribution. It has also been proposed that the distribution of affected blood vessels — predominantly in the superficial subcutaneous plexus (found in the papillary dermis)— results in the net-like pattern of erythema ab igne skin lesions.