Hello Doc, I had an anaphylactic incident on May 15th, and was treated with injection on the day, followed with anti-histamine tablets for 5 days. Then I missed my periods. It would have occurred on 22 May on a normal cycle, but I still have not have periods until 3rd June ( delayed by 12 days). I am worried if its because of adrenaline and anti-histamine medication! However, I have had these anaphylaxis incidents before also and given the same treatment but period was not delayed.