ICD-9 Coding for Allergy

When a 900 series code is used (i.e., 995.7) my billing system requires I enter an incident date and other related information. I thought these codes were for acute "incidents" not ongoing allergies. For example, if a person eats shellfish and gets hive and seeks treatment then I would use 995.7 and 708.0. But in 6 months when they come back in for a follow-up visit I would 693.1.

I wanted to get some opinion before I suggest this method of coding to my physician who is using a lot of 900 codes for ongoing treatment unrelated to an actual allergic event.