From your history it does seem like an exacerbation fo the allergy
. Rubbing of the eyes in anyone with the history of allergies is a bad idea as it releases more allergy inducing agent.
U can try some cold
compressess for him. also avoid exposure to any know allergen. do not rub the eyes again.
if he;s not ok in a day or two or develops any worsening, then you may consult a eye specialist. otherwise the scheduled appointment should be fine.
hope he gets welll soon.