Painless Lump On Back Of Ear, Dark Color Like Blood Blister. History Of Hypothyroidism. No Injuries.
Thanks for your query.
Based on the history suggested by you, I feel that this could be an insect bite reaction.
The history is acute that is it was not at night and erupted in your sleep. And presence of blood blister is more indication of a reaction to the insect sting or the toxins present on insect body.
It should subside in a week’s time. Insect bite reactions initially turn dark and then slowly fade away.
If there is no itching or pain, you need not be concerned. You can apply a mild steroidal cream to relieve you off your symptoms (if you have them) as well as to hasten the healing.
Hope I have provided you with good and useful information to answer your query satisfactorily. Please accept my answer if you do not have any further follow up.
Regards
Dr.Rohit Batra