C Unclear or conflicting scientific evidence
- Biotin : Biotin is an essential water-soluble B vitamin. Biotin has been suggested as a treatment for brittle fingernails, particularly in women. There is not sufficient scientific evidence to form a clear conclusion.
- Avoid if hypersensitive to constituents of biotin supplements.
- Bitter orange : Limited available human study found promising results using the oil of bitter orange for treatment of fungal infections. However, due to methodological weakness of this research, further evidence is needed to confirm these results.
- Avoid if allergic or hypersensitive to bitter orange or any members of the Rutaceae family. Avoid with heart disease, narrow-angel glaucoma, intestinal colic, or long QT interval syndrome. Avoid if taking anti-adrenergic agents, beta-blockers, QT-interval prolonging drugs, monoamine oxidase inhibitors (MAOIs), stimulants, or honey. Use cautiously with headache, hyperthyroidism (overactive thyroid), or if fair-skinned. Avoid if pregnant or breastfeeding.
- Cranberry : Limited laboratory research has examined the antifungal activity of cranberry. Reliable human studies supporting the use of cranberry for fungal infections are currently lacking. Further research is warranted in this area.
- Avoid if allergic to cranberries, blueberries, or other plants of the Vaccinium species. Sweetened cranberry juice may affect blood sugar levels. Use cautiously with a history of kidney stones. Pregnant and breastfeeding women should avoid cranberry in higher amounts than what is typically found in foods.
- Garlic : Garlic is used both medicinally and as a food spice. Several studies describe the use of garlic as a topical antifungal to treat fungal infections of the skin, including yeast infections. More research is needed in this area.
- Use cautiously as garlic can cause severe burns and rash when applied to the skin of sensitive individuals. Avoid if allergic or hypersensitive to garlic or other members of the Lilaceae (lily) family (e.g. hyacinth, tulip, onion, leek, or chive). Avoid with a history of bleeding problems, asthma, diabetes, low blood pressure, or thyroid disorders. Stop using supplemental garlic two weeks before and immediately after dental/surgical/diagnostic procedures with bleeding risks. Avoid in supplemental doses if pregnant or breastfeeding.
- Lavender : Early laboratory studies suggest that lavender oils may have topical antibiotic activity. However, this has not been well tested in human studies.
- Avoid if allergic or hypersensitive to lavender. Avoid with a history of seizures, bleeding disorders, eating disorders (such as anorexia or bulimia), or anemia (low levels of iron). Avoid if pregnant or breastfeeding.
- Propolis : Propolis is a natural resin created by bees to make their hives. Propolis is made from the buds of conifer and poplar trees and combined with beeswax and other bee secretions. Animal and laboratory studies suggest that propolis may be a beneficial treatment for various types of bacterial infections. Additional research is needed to confirm these findings.
- Avoid if allergic or hypersensitive to propolis, black poplar (Populas nigra), poplar bud, bee stings, bee products, honey, or Balsam of Peru. Severe allergic reactions have been reported. There has been one report of kidney failure with the ingestion of propolis that improved upon discontinuing therapy and deteriorated with re-exposure. Avoid if pregnant or breastfeeding because of the high alcohol content in some products.
- Seaweed, kelp, bladderwrack : Bladderwrack (Fucus vesiculosus) is a brown seaweed found along the northern coasts of the Atlantic and Pacific oceans and North and Baltic seas. Another seaweed that grows alongside bladderwrack is Ascophyllum nodosum, and it is often combined with bladderwrack in kelp preparations. Laboratory research suggests that bladderwrack may have antifungal activity. However, reliable human studies to support this use are currently lacking in the available literature.
- Avoid if allergic or hypersensitive to Fucus vesiculosus or iodine. Avoid with a history of thyroid disease, bleeding, acne, kidney disease, blood clots, nerve disorders, high blood pressure, stroke, or diabetes. Avoid if pregnant or breastfeeding.
- Tea tree oil : Although tea tree oil has been found to have antifungal activity against several fungus species in laboratory study, there is currently insufficient human evidence to determine if it is an effective topical treatment for this indication. Additional study is needed in this area.
- Tea tree oil may be toxic when taken by mouth and therefore, should not be swallowed. Avoid if allergic to tea tree oil or plants of the Myrtle (Myrtaceae) family, Balsam of Peru, or benzoin. Use cautiously with a history of eczema. Avoid if pregnant or breastfeeding.
- Thyme : Thyme has been used medicinally for thousands of years. Beyond its common culinary application, it has been recommended for many indications based on proposed antimicrobial, antitussive, spasmolytic, and antioxidant activity. Thyme essential oil and thymol have been shown to have antifungal effects. Topical thymol has been used traditionally to treat paronychia (skin infection around a finger or toenail) and onycholysis (fungal nail infection). Currently, there is insufficient reliable human evidence to recommend for or against the use of thyme or thymol as a treatment for fungal infections.
- Avoid if allergic or hypersensitive to thyme, members of the Lamiaceae (mint) family, any component of thyme, or rosemary (Rosmarinus officinalis). Avoid oral ingestion or non-diluted topical application of thyme oil due to potential toxicity. Avoid topical preparations in areas of skin breakdown or injury or in atopic patients due to multiple reports of contact dermatitis. Use cautiously with gastrointestinal irritation or peptic ulcer disease due to anecdotal reports of gastrointestinal irritation. Use cautiously with thyroid disorders due to observed anti-thyrotropic effects in animal research of the related species Thymus serpyllum. Avoid if pregnant or breastfeeding.