No, shift allowance is normally based on the no.of shifts attended and better to keep this away from CTC. In general there will be different pattern for different shifts ie., employees attending in First and General shift are not generally eligible for shift allowance. The employees who are reporting the Second and Night shift are going to be paid the shift allowance.
The shift duties are to be in rotation, on public holidays & weekly offs the employees shall be paid OT on double the rate hence in general the companies won't pay shift allowance in their shifts. Some times the employees will exchange the shift duties mutually.
If you include the shift allowance in CTC, irrespective of their shift duties they are eligible for that particular allowance and it will become part of their salary.
Considering the above points including the shift allowance in the CTC is not advisable.
Regards - kamesh