Garlic is

Garlic is an irritant to the stomach and kidneys, and is best left out of the dietary, unless used in minute quantities as a flavoring agent.It is claimed that, because of the sulphur content in garlic, it acts as an antiseptic for the intestinal and respiratory tracts, but eating enough garlic to disinfect these large body regions will do more harm than good.
Besides , when the intestinal or respiratory tracts really need disinfecting, we now possess the real thing in such drugs as penicillin and streptomycin.
The claim that an exctract of the active principle of garlic will reduce high blood pressure has not been proved as valid.