You needs to create table as below
1) metadata table which contains all allergy information in detail
2)Patient Details table to same name, age etc.
3) Patient_Allergies table which contains foreign key to both tables and multiple entries for same patient. You can also store more info like from date to date, timestamp if required.
Some useful links
How to bind Check box list,with example[
^]
required field validation with checkboxlist[
^]