A homogeniser (1) for the continuous treatment of fluids at very high pressure comprises at least one reciprocating plunger (5) in a compression chamber (6) and a guide chamber (11) from a fluid intake position to a delivery position. Said compression chamber (6) opens into a manifold (27), inside a block (26) from which a delivery pipe (32) and an intake pipe (31) branch off. A first seal unit (21) is housed in the guide chamber (11), a second seal unit (24) is located close to the intersection between the compression chamber (6) and the guide chamber (11) and a third seal unit (35) is positioned upstream and downstream of each valve (28, 29) and the intersection between the manifold (27) and the compression chamber (6).