Abstract: Characterised by the way it moves, in a column, the pine processionary caterpillar is a defoliating insect from the Lepidoptera order which causes extensive damage in forests. It can also provoke clinical problems in companion and leisure animals as well as farm animals. Humans can also be affected. Contact with the caterpillar's urticant hairs can cause buccal, skin and ocular problems as well as allergic reactions. This paper summaries the nuisance which is associated with the geographical expansion of the caterpillar and the possible treatments.