Side effects of hawthorn include rash, headache, mild-to-moderate dizziness and heart palpitations. Nausea, upset stomach and various intestinal symptoms may occur, according to Drugs.com. Some people have experienced fatigue, sweating, palpitations, nosebleeds and insomnia, states WebMD.
Hawthorn rarely causes any severe side effects, although it may have serious interactions with some prescription medicines, states WebMD. For this reason, people taking other medicines or supplements should consult a health care provider before taking hawthorn. Pregnant or nursing women should avoid hawthorn to be safe, as it is not known if it is potentially harmful, as of 2015. People with heart conditions should not take hawthorn unless specifically directed by a physician.
Some people take hawthorn to treat conditions related to the heart or blood vessels, such as irregular heartbeat, chest pain and congestive heart failure, notes WebMD. Hawthorn may be taken to counteract diarrhea, stomach pain or indigestion. Hawthorn is also used to treat anxiety, and it is used as a sedative and to relieve the symptoms associated with premenstrual syndrome.
Hawthorn may be taken for intestinal infections, such as tapeworm, according to WebMD. It may be applied topically to treat ulcers, sores and boils. Research suggests that hawthorn may help with lowering blood pressure by relaxing blood vessels. It may lower triglycerides, low density lipoprotein and cholesterol. As of 2015, research is ongoing to verify the efficacy of hawthorn for these various applications.