Would it be PUT /patient/{uuid}/allergies with an empty list? If so, that should return a 400 error if the patient has any known allergies (we shouldn’t silently void existing allergies).
A problem is this will not allow a patient to move from having allergies to no known allergies if we need to support this. A child might be allergic and grow out of it. The allergies may have been attached by mistake and have to be removed.
It seems we need to differentiate the initial state and the state that is empty, from an explicit void state. If we start with Unknown Status and return to Unknown Status when all Allergies are voided, then we must be able to set No Known Allergies at any time irrespective of whether there are attached allergies or not.
As @Wyclif indicates the webservices infrastructure does not support
DELETE /patient/{uuid}/allergy would set the allergy list to an unknown status (i.e., we don’t know anything about the patient’s allergies)
it may support
PUT /patient/{uuid}/allergies with an empty list
however.