No. No reason why it should.
Our 15yo daughter was recently started on birth control pills to control her menstrual cycle and pain. Approximately 2 weeks ago. She has started to break out with welps all over her body that itch tremendously. Benadryl alleviates the symptoms quic
Causation likely. Hormonal influences are well-recognized triggers for hives. If the bcp is essential you may want to consider switching her to a longer-acting anti-h1.
Could 3 Benadryl (diphenhydramine) Allergy (acrivastine) capsules per day cause a change in menstrual cycle; mid-cycle (around ovulation time) bleeding and late period?
No. I am not aware of antihistamine use affecting menstrual cycles. You need to consult your gynecologist and perhaps even an allergist for your allergies.