According to most sources, red raspberry has no known counter-indications or side effects.  However, there are several websites, including MDidea.com, as well as many medical doctors, that caution against using raspberry leaf during the first trimester.  The rationale is that because it can stimulate uterine tissue in vitro, it may stimulate contractions and cause a miscarriage.  This concern, however, does not seem to be problematic because raspberry leaf has been known to quell premature contractions, Braxton-hicks contractions, and many midwives recommend it for the prevention of miscarriage.

Natural Standard mentions that in vitro studies of a methanol extract of raspberry leaves have shown a muscle relaxant activity.  It also cautions against using raspberry along with the antifungal clotrimoxazole because it seems to increase the bioavailability of the drug.  Another drug interaction is due to antibiotic activity in raspberry.  Raspberry taken with antibiotics, especially clarithromycin, seems to interact additively.  Therefore, Natural Standard advises caution.[1]

The berries should be thoroughly washed to prevent food-borne illnesses.