According to WebMD, flaxseed oil is mostly safe for adults to use when used appropriately for a short period of time. Doses of 30 milligrams daily or more may result in loose stools and diarrhea. Allergic reactions have also been documented from taking flaxseed oil.
According to WebMD, there is not substantial knowledge regarding effects of flaxseed oil when applied to the skin. Flaxseed oil may be unsafe to use during pregnancy. Some research indicates that using flaxseed oil during pregnancy may heighten the likelihood of premature birth when used during the second or third trimesters. According to WebMD, caution should also be exercised by people who have bleeding disorders when taking flaxseed oil, as the oil may augment the chance of severe bleeding.