Absolutely. You can never let your guard down, and it sounds like you are doing a great job.
One more suggestion from someone who has been there. Have your son avoid using aspirin for pain if possible. Here is why I say this.
All my life, when I would have a reaction to unwittingly eating something I was allergic to, I was usually able to control it with a stiff dose of benadryl or atarax. However, there were a couple of times that we had to call an ambulance. It's just my nature to try to figure out what was different about those occasions. On one of them I recalled that I had taken a couple of aspirin shortly before dinner. So, on a lark, I decided to see if there was any chance that aspirin was known to affect the anaphylactic process.
To my utter shock (shock because my doctors never told me), I found evidence that it was. I wouldn't say this is well-established (it still isn't) but there are reports that aspirin enhances the allergic response. This is still the best explanation for one of my very unpleasant and expensive treks to the emergency room. This is getting long so I will post a couple refs in the next message.
Here are some references. If you click on the link, you will find more there on food allergy and aspirin.
1. Food anaphylaxis induced by aspirin. Allerg Immunol (Paris). 2001
Mar;33(3):147-9.
2. [A clinical case of 13 years old boy of aspirin-induced asthma with food
allergy] Arerugi. 2000 Nov;49(11):1104-7. Review.
3. Dramatic augmentation of a food allergy by acetylsalicylic acid. J
Allergy Clin Immunol. 2000 Apr;105(4):844. .
4. Aspirin enhances the induction of type I allergic symptoms when combined
with food and exercise in patients with food-dependent exercise-induced
anaphylaxis. Br J Dermatol. 2001 Aug;145(2):336-9. (full text should be free
online check link below)
We examined the effect of aspirin as a substitute for exercise in inducing
urticaria/anaphylaxis in three patients with food-dependent exercise-induced
anaphylaxis (FDEIA). Two of the patients had specific IgE antibodies to
wheat and the other had antibodies to shrimp. Administration of aspirin
before ingestion of food allergens induced urticaria in one patient and
urticaria and hypotension in another, while aspirin alone or food alone
elicited no response. The third patient developed urticaria only when he
took all three items, i.e. aspirin, food and additional exercise, whereas
provocation with any one or or two of these did not induce any symptoms.
These findings suggest that aspirin upregulates type I allergic responses to
food in patients with FDEIA, and further shows that aspirin synergizes with
exercise to provoke symptoms of FDEIA. This is the first report of a
synergistic effect of aspirin in inducing urticaria/anaphylaxis, which was
confirmed using challenge tests in patients with FDEIA.
http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-2133.2001.04329.x