Exposure to larvae of pine processionary caterpillar (Thaumetopoea pityocampa), usually by direct contact, leads to a rapid and exuberant allergic response to caterpillar's hairs, rich in thaumetopoein. In dogs, clinical signs include lingual, sublingual and submandibular oedema, facial pruritus, ptyalism, vomiting, and sometimes ocular signs. The most frequent sequel is partial lost of the tongue, following a necrotizing process. In the present case, the lesions developed in two-stages, with 4-days interval. A 10-months old bitch was presented five hours after contact with Thaumetopoea pityocampa with a history of sudden ptyalism, vomiting and facial pruritus. She showed lingual necrosis and severe discomfort. Oral cavity was flushed with pressurized water, to eliminate the majority of urticating hairs. Methylprednisolone sodium succinate and amoxicillin/clavulamic acid were administered. By the third day, the necrotized portion of the tongue was lost and the animal apparently recovered, eating normally. By the fourth day, she stopped eating and lesions of labial and mentum necrosis were noticed, accompanied by conjunctival hyperemia and corneal ulceration. Muzzle clipping and local disinfection were performed, treatment was maintained and the animal was fed through a nasogastric tube. A topical ointment of chloramphenicol was applied TID in the eye. Necrotized tissues were gradually eliminated. The animal was discharged 5 days later, with labial and lingual lost. This case's evolution is very atypical, with lesions developing in two-stages, with a 4-day interval. The late labial and mentum involvement is consistent with a continuous liberation of thaumatopoein persisting in the long hair of the animals' muzzle.