Garlic is widely used for flavoring food, but it can also be used as a medicine. Garlic can prevent and treat many different diseases connected with the heart and blood system: high cholesterol, high blood pressure, heart attack, coronary heart disease, and "hardening of the arteries" (atherosclerosis). Garlic shows effectiveness in slowing atherosclerosis and reducing blood pressure.
This plant can also be used to prevent colon cancer, stomach cancer, rectal cancer, prostate cancer, breast cancer, bladder cancer, and lung cancer. Garlic can effectively reduce an enlarged prostate, treat diabetes, hayfever, osteoarthritis, traveler's diarrhea, high blood pressure in the third trimester of pregnancy, cold and flu. It enhances the immune system, prevents bacterial and fungal infections, as well as tick bites.
It's no less useful in case of fever, headache, coughs, stomach ache, gout, sinus congestion, rheumatism, asthma, hemorrhoids, bronchitis, low blood pressure, shortness of breath, high blood sugar, low blood sugar, and snakebites. Garlic contains allicin which is an active ingredient of this vegetable and determines its smell.

Garlic is safe for most people even though it causes bad breath, heartburn and a burning sensation in the stomach or mouth. However, there are some other side effects of garlic namely gas, nausea, body odor, vomiting, and diarrhea. Raw garlic worsens these side effects. It may also increase bleeding in case of any traumas so it should be avoided after surgery. Asthma may also be provoked by garlic.
When applied to the skin, garlic is unsafe as it can cause damage of the skin burning it. Garlic is considered to be safe when used during pregnancy if it is taken in the amounts found in food. But it can be unsafe when used in medicinal amounts during pregnancy and breast-feeding.
Garlic is safe when taken from time to time by mouth by children but it can be unsafe when taken in large quantities. Some sources say it can be fatal to children if overdosed. Garlic in the fresh form might increase bleeding so it should be avoided after surgery. It can irritate the gastrointestinal tract.