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El ajo

Phytotherapy Blog


Garlic (Allium sativum) is a plant, used in Spain as food since Middle Ages. Introduced in Spain firstly with medical purposes, garlic prevents and helps the treatment of many diseases.

Its main active substance is Allicin, that is also responsible of garlic's strong odour. Therefore preparations with old garlic (without odour) are considered to be doubtful, because they barely containing allicine.


Garlic, through allicin and ajoene, is a powerful antimicrobial. It also has an important anticoagulant and hypoglycemic effect. Garlic is also present in vampire's legends without a real reason because garlic's consumption may scare away some insects, being partially eliminated through the skin.

According to US National Library of Medicine and Fitoterapia.net webpage, garlic is potentially effective in the treatment of the following conditions:

  • Atherosclerosis: it seems that garlic reduces the effect of loose arteries, in terms of elasticity, casues by aging.
  • Stomach, colon and rectum cancer: it seems like this effect it connected to the consumption of fresh garlic (allicin), thanks to its antimicrobial effect. We remind you that many types of cancer are produced by microorganisms. In studies realized in laboratory, there's evidence that proves that allicin kills some enterobacteiaceae (bacteria of the digestive tract).
  • Intestinal parasitic infections: it seems to help in pinworms infections.
  • High blood pressure: garlic seems to reduce blood pressure in peoplo suffering from mild or moderate hypertension.
  • Picaduras de insectos: consumir altas dosis de ajo habitualmente parece reducir el número de picaduras de garrapata, mosquitos y otros insectos (aunque hay cierta controversia al respecto).
  • Tinea pedis or athlet's foot (skin infection produced by fungus): application of gels with ajoene (substance present in garlic) seems to be effective like others antifungals in fungi treatment.
  • Urinary infections: the principal way of garlic excretion is through kidneys; it seems like garlic interacts with bacteria of the urinary tract.
  • Hyperlipidemia: it seems like garlic hyperlipidemia treatment.
  • Cold: it seems like there's controversy about this garlic's property, according to different studies.


PREGNANCY AND BREASTFEEDING: Garlic IS POSSIBLY SAFE in most pregnant women, if taken in normal quantities, as present in food. Women must not take garlic based supplements, without previously consulting their gynecologist, considering that garlic IS NOT POSSIBLY SAFE during pregnangcy and breastfeeding if taken in big quantities.

KIDS: Do not give garlic in big dosis to kids without consulting a doctor. Garlic IS POSSIBLY SAFE for kids if taken by mouth and properly for a short term.


Medications and plants based supplements, even if most people believe the contrary, have contraindications and can interact with other medications, therefore it must always be taken into consideration possible preventive measure, like consulting your doctor or pharmacist, considering the complexity of the possible adverse effects in many cases.

Here it is a list of medications with whom garlic interacts:

SERIOUS. Do not take together with:

  • Isoniazid
  • Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) like nevirapine, delavirdine or efavirenz.
  • Saquinavir

MODERATE. Consult your doctor before taking garlic together with:

  • Cyclosporine
  • Cytochrome P450 substrate (garlic can increase or decrease drug metabolism time) like: paracetamol, chlorzoxazone, ethanol, theophylline, drugs used in surgery like como enflurane, halothane, isoflurane and methoxyflurane, Calcium channel blocker (diltiazem, nicardipine, verapamil), cancer drugs (etoposide, paclitaxel, vinblastine, vincristina, vindesine), antifungal drugs (ketoconazole, itraconazole), glucocorticoids, alfentanyl, cisapride, fentanyl, lidocaine, losartan, midazolam and others.
  • Antihypertensives (garlic can increase the effect): nifedipine, verapamil, diltiazem, isradipine, felodipine and amlodipine. 
  • Anticoagulants (garlic can increase puede aumentar the anticoagulant effect): aspirin, clopidogrel, diclofenac, ibuprofene, naproxen, dalteparin, enoxaparin, heparin, warfarin and others.
  • Contraceptives (garlic can decrease the effectiveness, therfore the use of a condom is suggested) ethinylestradiol and levonorgestrel, ethinylestradiol and norethindrone and others.
  • Warfarine (garlic can increase warfarine effect)




Amapola Munuera

MSc in Pharmacy