benadryl (diphenhydramine) does not cause a fever nor is fever an adverse reaction to this antihistamine. allergies do not cause fever so any elevation in temperature that may have experienced is most likely do to your cold (assuming you have correctly diagnosed yourself). fever is the body's natural response to fighting off an infection.
runny nose took antihistamine. developed fever. reaction to drug or cold/allergy symptom? . took over the counter diphenhydramine hci 25 mg. no fever prior to taking it but i had a bad runny nose.