- Oat
- Ocimum basilicum
- Ocimum gratissimum
- Ocimum tenuiflorum
- Oenanthe pimpinelloides
- Oenothera biennis
- Oenothera fruticosa
- Oldenlandia umbellata
- Olea capensis
- Olea europaea
- Olive
- Onion
- Onoclea sensibilis
- Ononis repens
- Ononis rotundifolia
- Ononis spinosa
- Onopordum acanthium
- Onopordum illyricum
- Ophioglossum lusitanicum
- Ophioglossum vulgatum
- Ophrys insectifera
- Orchis mascula
- Orchis militaris
- Oregano
- Origanum dictamnus
- Origanum majorana
- Origanum onites
- Origanum syriacum
- Origanum vulgare
- Ornithogalum arabicum
- Ornithogalum nutans
- Ornithogalum pyrenaicum
- Ornithogalum umbellatum
- Ornithopus perpusillus
- Orobanche ramosa
- Orobanche uniflora
- Orontium aquaticum
- Oroxylum indicum
- Oryza sativa
- Osbeckia chinensis
- Osmunda claytoniana
- Osmunda regalis
- Osmundastrum cinnamomeum
- Osyris alba
- Ovieda spinosa
- Oxalis acetosella
- Oxalis corniculata
- Oxalis incarnata
- Oxalis pes-caprae
- Oxalis purpurea
- Oxalis stricta
- Oxalis violacea
- Oxybasis glauca
- Oxybasis rubra
Origanum vulgare
- Oregano (Origanum vulgare, also known as marjoram)
- Used for: digestion, headache, colic, "nervous complaints", coughs and respiratory ailments, menstrual cramps,<wiki/List_of_medicinal_plants#cite_note-theherbbook-7"> and vaginal steaming
- Benefits:
- Studies show long-term use of oregano may reduce high cholesterol.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- Studies show long-term use of oregano may kill the stomach parasites Blastocystis hominis, Entamoeba hartmanni, and Endolimax nana.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- Non-benefits:
- A study suggested that oregano did not prevent bleeding in people with hemophilia.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- A study suggested that oregano did not speed or aid the wound healing process, though it did reduce skin stiffness and improve skin color.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- Research: No other major research on oregano's health benefits has been conducted. Despite contrary claims, oregano has not been shown to help asthma, bronchitis, coughing, the flu, indigestion, painful menstrual periods, arthritis, headaches, or heart conditions.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- Harmful effects:
- Oregano is probably safe in food quantities.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- Oregano is possibly unsafe in medicinal quantities during pregnancy, and may possibly cause miscarriage.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- Oregano may increase the risk of bleeding, which may be problematic before surgery and in people with bleeding disorders.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- Oregano can lower blood sugar levels, potentially problematic for diabetics.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- People can be allergic to oregano.<wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
- Oregano is a diuretic. <wiki/List_of_medicinal_plants#cite_note-WebMDOregano-170">
Oenothera biennis
- Evening primrose oil (Oenothera spp.)
- Usage: Used for treatment of coughs and colds, depression, and skin irritation.<wiki/List_of_medicinal_plants#cite_note-theherbbook-7"> Useless for eczema,<wiki/List_of_medicinal_plants#cite_note-92"> but may help with breast pain.<wiki/List_of_medicinal_plants#cite_note-epo-93"> Insufficient evidence for any other conditions.
- Harmful effects: Side effects may include upset stomach, nausea, diarrhea, and headache.<wiki/List_of_medicinal_plants#cite_note-epo-93">
Ocimum basilicum
- Basil (Ocimum basilicum); in TCM: luólè (羅勒):<wiki/List_of_medicinal_plants#cite_note-read-12">
- Usage: vaginal steaming
- Claimed to: reduce spasms, help expel farts, increase milk production, and it's tasty!<wiki/List_of_medicinal_plants#cite_note-theherbbook-7"> It has also been said to be spiritually cleansing.
- Beneficial effects: In vitro, has been shown to be antioxidant, antiviral, and antimicrobial.<wiki/List_of_medicinal_plants#cite_note-pmid16506839-21"><wiki/List_of_medicinal_plants#cite_note-pmid16173941-22"><wiki/List_of_medicinal_plants#cite_note-pmid17342533-23"><wiki/List_of_medicinal_plants#cite_note-pmid15979235-24"> No clinical studies, yet, however.
- Harmful effects: Lowers blood pressure and prevents clotting, which situationally might be good but is often bad. Little efficacy otherwise.<wiki/List_of_medicinal_plants#cite_note-25">
riganum vulgare oil
- Oil of oregano (Origanum vulgare, also known as marjoram oil)
- Used as: an anti-fungal, anti-viral, anti-bacterial, abortifactant, anti-asthma, anti-malaria, antioxidant and anti-cold/flu/headache medication (take your pick). While it has a higher rate of success on malaria and bacteria on the skin than normal water, it has significantly less success than any standard over-the-counter antibiotic or medicinal anti-malaria drug.<wiki/List_of_medicinal_plants#cite_note-165"> As with most woo, there is always a glint of truth that gets warped into $$$$$.<wiki/List_of_medicinal_plants#cite_note-166"> It is a good antioxidant, but not more so than raw oregano, which tastes better and makes wicked salads. And, despite its name, it tastes absolutely foul (as this user will attest).
- Harmful effects: Side effects may include gastrointestinal issues and allergic reactions.<wiki/Help:References" title="Help:References">