While grape seed extract side effects are generally very mild, a number of gastrointestinal and upper respiratory reactions have been reported. Mild vertigo, dry skin, and headaches may also occur. In addition, this supplement may cause adverse reactions in patients who take certain medications and those with specific illnesses. As with most medicines, allergic reactions are also possible.
Upset stomach and indigestion are the most commonly noted side effects of grape seed extract. In rare instances, these symptoms may be accompanied by nausea and diarrhea. These complaints most commonly occur shortly after beginning a grape seed oil regimen and vanish within a few days.
Individuals who take grape seed extract may experience a sore throat and mild cough. Elevations in blood pressure may also occur in some patients, leading to dizziness and headaches. In addition, skin ailments, especially dry scalp, occasionally arise after taking this medication. If these conditions are severe or they do not dissipate within a few days, individuals are advised to discontinue this medication and contact a medical professional.
Rarely, grape seed extract side effects may include potentially dangerous interactions with other medications. The same compounds in the supplement that may improve circulation can also prevent blood from clotting normally. People who take blood thinners, such as warfarin or heparin, are generally advised to avoid grape seed extract. Care should also be taken when mixing the herb with over-the-counter medicines, including aspirin or ibuprofen.
Patients with blood clotting disorders, such as hemophilia, should also avoid grape seed extract. The use of this herb by these individuals may increase the chances of spontaneous internal hemorrhage. Unexplained bruising, bloody stools, and the vomiting of blood may indicate internal bleeding.
Very rarely, people taking grape seed oil may experience allergic reactions. Symptoms of these reactions occur shortly after taking the supplement and may include mild to moderate skin irritation and itching. Indications of a severe allergic reaction include swelling in or around the mouth and throat and difficulty breathing. People experiencing these symptoms are advised to seek immediate medical attention.
Children and the elderly seem to be most susceptible to grape seed extract side effects. As such, these individuals should only use the supplement if advised by a healthcare professional. Additionally, pregnant or nursing women should avoid grape seed as there are too few studies to establish its safe usage in these groups.