The distinctive smell on the breath and even seeping from the pores of those who eat a great deal of garlic is the herb's most familiar side effect and the one that prompted garlic's nickname since Greek and Roman times: "The Stinking Rose." Garlic has long been used for medicinal purposes as well as flavor, but it can cause serious side effects and may even interact in a dangerous way with certain prescription and over-the-counter drugs.
Most-Noticed Side Effect: Odor
The smell of a garlic-rich meal or doses of raw garlic can linger for days. Some suggest chewing fresh parsley with a garlic meal or consuming cardamom as a breath-freshener, although many find the strong taste of cardamom worse than the garlic. Those who take garlic for health reasons may resort to taking the oil in capsule form.
Those who are sensitive to some of the compounds in garlic can develop nausea. Experts suggest that eating more than 10 cloves of garlic per day can cause reactions even in those not normally allergic.
The symptoms of sensitivity to garlic are a burning sensation in the mouth, throat or stomach, dizziness, nausea and sweating.
More intense side effects may be signs of a serious allergy that demands immediate medical attention. Such symptoms include shortness of breath, swelling of the mouth, face, lips or tongue, tightness in the chest, itching, rash or hives.
Nursing mothers should be cautious about consuming garlic--infants who drink breast-milk containing garlic can develop colic.
The most popular way to consume garlic is to chop it up raw and use it in cooking or to or eat the raw cloves directly. The sulfur in garlic makes it a fertile breeding ground for botulism (clostridium botulinum), which can cause severe stomach upset and even death. Experts warn to never store garlic in oil at room temperature. Commercially prepared minced garlic that lists salt and acids as contents should be safe if stored in the refrigerator and not used past the expiration date.
The blood-thinning action of garlic that leads people to take it for heart problems can cause bleeding or inhibit blood clotting for those on blood-thinning medications. Garlic can intensify oral anticoagulant and/or anti-platelet prescriptions such as heparin or heparin-like products. Similar cautions about possible bleeding or stomach upset problems are urged for those who take aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs).
Garlic Weakens Some Prescription Drugs
Those who are on birth control pills, isoniazid or immune suppressors such as cyclosporine should consult with a healthcare provider before taking garlic supplements or consuming large amounts of garlic in food--garlic has been proven to reduce the effectiveness of these drugs.
Garlic Interferes with Protease Inhibitors
Doctors began urging patients on protease inhibitors to avoid garlic supplements after a 2001 study looked at the use of garlic caplets. Garlic had become a popular natural supplement among patients who developed higher cholesterol as a side effect of HIV medications. Unfortunately, garlic caused a dramatic 51 percent decrease in the protease inhibitor saquinavir, one of several drugs often given to slow the progression of HIV infection. Researchers concluded garlic may have a similar effect on other protease inhibiting drugs.