If you haven't already:
Click Write (ALT+W).
Click Allergies/Adverse Reactions (ALT+L).
To indicate that the patient has no known allergies:
If the record currently holds specific allergies in error, discontinue these to reactivate the NKA button. Select each order and click D/C (ALT+D).
Click NKA (ALT+K)
Click Close (ALT+C).
Other allergy options:
Write additional orders as needed, then sign the session.