Your friend is obviously facing some kind of food craving but instead of snacking on junk food, garlic seems to be craving of choice here. The good news is that garlic is quite harmless in most cases unless ingested in really huge quantities. This would be the case if your friend was ingesting four cloves of garlic at each sitting many times a day. The most likely reasons for this slightly odd craving is that your friend might have read articles much like this one that propagated the health benefits of having garlic. This is not entirely unfounded either. In the natural world, there are few more potent antibiotics and antifungal medicines than garlic. It is effective against viruses also but the concentrations that it has to been eaten in would be lethal. You don’t have to worry about your friend having garlic in lethal doses because the body would immediately expel a toxic amount of garlic by inducing vomiting. On the good side, your friend would be acne free and probably free of a lot of bacterial infections for a while. If this is really a point of concern for you, you could tell your friend about some of the bad sides of garlic.
Garlic belongs to the family of onions called the allium family and the active ingredient of interest in it is allacin – the antibiotic. However, there are an entire bunch of compounds that are also within garlic and just like onions garlic also contains a form of mercaptan. This is a gas that is release when the plant and bulb is damaged, it causes irritation and lacrimation, the production of tears. When you eat a garlic, just like an onion, the first effect is that on the breath. This is however not restricted to just the breath as the gaseous mercaptans will diffuse from the blood stream out of the skin as well giving the whole person a slightly foul odor. Garlic also contains chemicals that can reduce blood pressure. When taken in an overdose, it could then cause a massive drop in blood pressure that can cause malaise and fainting spells. Beyond this, garlic is contraindicated with the use of some types of drugs like antiviral drugs, blood thinning drugs, and antihypertensives. Considering all these, it is probably better to limit the consumption of garlic to just one bulb a day as that would be a healthy amount to indulge in.