Cyclic relationships in ER Diagrams
Yes it is acceptable.  In ER modeling, this is known as a reflexive relationship.  In a relational model, it's implemented by a foreign key that references another row in the same table.  

The simplest example is a table of employees, where the PK is EmployeeID (or just ID) and there is an FK called SupervisorID.  This kind of thing is done all the time.