How to manage the clinical evolution of the "allery" status

As you know, we're trying to implement SCT to capture allergies in our EHRs. Our goal is to make clinical information reusable and to use it to trigger alerts and clinical pathways.
In our EHR, we have in the clinical notes and reports an "allergy" field where clinicians can document the presence or absence of an allergy (in the broad clinical sense, also the pseudoallergies). This field is what we call a "recurrent field" meaning that the information captured in this field goes to a central "permanent" patient summary, that can be viewed separately form the notes, and that whenever a clinician opens a new empty clinical note, the field allergy in this note will automatically be filled in with the allergy data already present in the patient summary.
Now this allergy field is not a free text field but linked to a dictionnary of terms (that can be updated if some clinicians detect a missing term or expression). Previously it was a rather bad ICD-based dictionnary, so it wasn't much used. Now we work on a SCT-based dictionnary. A first basic dictionnary of 500 SCT-liked french terms is in production since August in a number of our participating institutions and we're working on adding more clinical expressions / concepts to it.

We had one term in the dictionnary that was "no known allergy". Now clinicians ask for more specific "no known allergy" terms that would include the causative agent, like no known allergy to latex. Because you could be allergic to penicilline and not allergic to latex and the surgeon would want to know that the question has been asked and you're not allergic to latex. So "no know allergy" for when the patient is allergic to nothing is not enough. We need also to record the absence of allergy to specific substances.

Now there are not many "no known allergy to X" SCT terms and I wonder even if there should be any. Should the negation, the absence of a disease or a finding not always be outside the terminology and be a postcoordination of the existing positive clinical concept?

If the negation is in the concept, precoordinated, when the patient becomes allergic, you can not consider this as an update to your existing entry, you have to create a new record line for the allergy and the old no known allergy to the same substance will remain visible as an "inactive" former "disease record". Clinicians find it confusing. They would wish the no known allergy entry to be "written over" if the patient becomes allergic to the same substance.

We have a similar "switch" problem between concepts with allergic reaction and allergic disposition. When you record an allergic reaction in the contact nr1, this diagnose will go to the patient summary but on the visit nr2, what you want to have in your problem list is the mention of an allergic disposition. And what you want is to get this allergic disposition to trigger warning when you prescribe exams, drugs or to the kitchen for the food given at the hospital. So in an EHR, you actually need a layer above SCT that will automatically switch from one concept to the other, from reaction to disposion, when you store the captured allergic reaction concept in the patient summary if you want to re-use your information in the patient summary in the next event and as trigger of clinical actions/pathways?

How is this handled in the EHRs that use SCT right now? Anyone knows? Any advice on whether I should put the negation outside my dictionnary (postco) or inside (using the few no known allergy concepts and creating eventually more of them locally)?

Thanks beforehands for your input.