Interne des Hôpitaux de Paris in 1844, Lailler was head of a dermatological department in
Saint-Louis hospital from 1863 until 1887.In 1863, Lailler discovered Jules Baretta, moulageur and creator of the wax moulages collection in Saint-Louis. In 1874, Lailler founded in his department a library for the students.
In 1878, he created a special school devoted to the teaching of children treated for tinea capitis previously forced to leave school because of contagiosity. The building where this school ("Ecole Lailler") stood is still visible today.
In 1891, he was elected as President of the French Society of Dermatology.