Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Although not all side effects are known, garlic is thought to be possibly safe when taken for a short period of time.
Stop using garlic and call your healthcare provider at once if you have:
redness, swelling, or blistering (when applied to the skin); or
easy bruising or bleeding (nosebleeds, bleeding gums).
Common side effects (especially when eating raw garlic) may include:
unpleasant breath or body odor;
heartburn, burning in your mouth or throat;
nausea, vomiting, gas or
diarrhea.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Garlic side effects (more detail)
