The effects of porphyrins and radiation on inflammation include activation of the complement system, generation eicosanoids from mast cells, macrophages, and endothelial cells, alteration in cutaneaous eicosanoid metabolism, activation of factor XII-dependent pathways, release of mediators from mast cells, and dermal accumulation of neutrophils. These effects contribute to the development of porphyrin-induced cutaneous inflammation, which can be seen in patients with porphyrias and as a consequence of photodynamic therapy.