The BSc MLS generally does not set an age bar for taking admission. Though there are, of course certain minimum age barriers such as at least 17 or 18 years as established by the different universities or institution granting the programme, to establish that the student is physically and mentally fit for the course with the clinical practice it entails.
Age is not a strong barrier, but applicants need to be conscious of other eligibility criteria, like academic qualifications, such as 10+2 or equivalent with science subjects, and an entrance exam or interview process at times. Institutions differ in their specifics of the admission policy, so it's always advisable to make separate searches according to each college or university prior to applying for the requirements to be matched.