Contact with the caterpillars of the pine processionary moth (CPPM) Thaumetopoea pityocampa induces severe local allergic reactions. The purpose of this large-scale retrospective cohort-study was to describe the clinical manifestations and related risk factors of CPPM exposure. This cohort-study included 109 dogs between the years of 2000 and 2016. Tongue lesions ranging from oedema to severe necrosis were observed in 94/109 dogs (86%). The following systemic signs were observed in 60/109 dogs (55%): vomiting (52/109, 48%), dyspnoea (6/109, 5%), hypovolemia (4/109, 4%) and diarrhoea (2/109, 2%). Based on the time elapsed from CPPM contact to the first oral flushing, three groups were defined: <2 h (group 1, 37/105, 35%), 2 h–6 h (group 2, 39/105, 37%) and >6 h (group 3, 29/105, 28%). Tongue necrosis (TN) at admission was significantly more common in the dogs in group 3 than those in groups 1 and 2 (45% vs. 5% and 5% respectively, p = 0.0002). In addition, the development of TN during hospitalisation was significantly more common in the dogs in group 3 (65%) than in those in the other groups (21% in group 1, p = 0.02) and 31% in group 2, p = 0.001). The dogs in group 3 presented a 14.63-fold higher risk of TN at admission and a 3.78-fold higher risk of developing necrosis during hospitalisation compared with the other groups. The survival rate after exposure was 97%. Long-term follow-up data were available for 69/109 dogs (63%). Twenty-three dogs (37%) had persistent, definitive TN without major consequences on quality of life. Elapsed time between contact and first oral flushing appears to be a key determinant for the progression of necrotic lesions, and the best results were observed when flushing occurred within 6 h of contact. The prognosis of CPPM envenomation is excellent, with a short hospitalisation duration.