Yes this is rare
Yes this is an odd occurrence, quite rare.
The possible reasons which I can think are::
*This is related to the part of the trigeminal nerve
, the distribution is, as well mentioned by you. This occurs as the nerve is stimulated for that period only.
This explains the non-pattern and occurrence for 3 to 4 days.
*Another possible reason can be related to an allergy
(and you are a known asthmatic) wherein one gets deposits of blood cells called eosinophils and gives this atypical presentation you have. That is why you are getting results with Benedryl
Do you ever take steroids
. Please discuss with your Doctor for a trial with Deflaxacort ( it is safe in hypertension
and helps in asthma also and taking for 1 to 3 weeks in reducing doses have minimal or no side effects) If this trial helps you, it is diagnostic and therapeutic too.