Aloe Vera

Aloe vera ( Aloe barbadensis ) is applied topically to treat a number of afflictions including thermal burns, ulcers or chronic wounds, and mild cutaneous infections . It has also been used successfully to treat psoriasis . Two products, a gel and a latex component, are derived from the aloe vera plant; it is the former that is used to treat cutaneous injuries or diseases. Active components of aloe vera include salicylic acid, magnesium lactate, and gel polysaccharides. When applied to the skin, its anti-inflammatory effects are thought to be due to a reduction in levels of thromboxane A2, thromboxane B2, and prostaglandin 2 . Although generally well tolerated, aloe vera gel may cause an allergic contact dermatitis.

Capsaicin

Capsaicin is found in hot peppers ( Capsicum ), and it is a mixture of vanillyl amides of isodecenoic acid. Topical capsaicin is used for postherpetic neuralgia, notalgia paresthetica, diabetic neuropathy, reflex sympathetic dystrophy, and hemodialysis-related pruritus. By binding to the vanilloid receptor-1 on pain fibers, capsaicin stimulates the release and eventual depletion of the neurotransmitter substance P. Prolonged exposure leads to deactivation of these neurons . While considered safe enough to appear in multiple over-the-counter preparations, the associated stinging and burning sensations can be very unpleasant, especially when applied to fissured or denuded skin and must be used with caution.

Chamomile

Chamomile ( Matricaria recutita ; Chamaemelum nobile) is used to treat mucocutaneous inflammation and to promote wound healing. It is traditionally used for dermatitis and may be applied topically or ingested as a tea. When applied topically, it has been shown to be beneficial in atopic dermatitis and nonspecific skin irritation. Chamomile contains terpenoids and flavonoids that inhibit cyclooxygenase and lipoxygenase as well as regulate T-helper-cell (Th2) activation and histamine release . Chamomile is a member of the ragweed family and has the potential to induce allergic contact dermatitis, as well as contact urticaria.

Colloidal Oatmeal

For decades, colloidal oatmeal has been used for its calming and soothing effects on the skin. Many over-the-counter products are derived from whole oat kernels ground into a fine powder and then combined with emollients to create various preparations from bath powders to moisturizing creams . Colloidal oatmeal is one of the few natural ingredients approved by the US Food and Drug Administration (FDA) for use as a treatment for skin conditions such as allergic contact dermatitis to poison ivy, irritant diaper dermatitis, and eczema.

The therapeutic properties of oats are thought to derive from its diverse chemical composition. Firstly, oats have a high concentration of starches which explains their water-holding function. Secondly, high concentrations of phenols give oatmeal antioxidant and anti-inflammatory properties. Lastly, its cleansing activity is thought to be due to the saponins present in the grain . Products that contain colloidal oatmeal tend to have very low allergenicity .

Escharotics

Escharotics include zinc chloride, bloodroot ( Sanguinaria canadensis) , and goldenseal ( Hydrastis canadensis ). These agents are caustic and can produce pain and necrotic crusts with subsequent scarring. In the past, escharotics were used topically to treat skin cancers and played a role in the fixed-tissue technique initially used in Mohs micrographic surgery, but they have since been replaced with more predictable and reliable methods. As escharotics are commercially available, unsupervised patient use may lead to potentially unfavorable results .

Feverfew

Feverfew ( Tanacetum parthenium ) is a flowering plant from the daisy family. Originally named for its fever-reducing properties, it is also used to treat headaches, arthritis, and digestive disorders. Use of topical feverfew had been limited by the presence of irritating parthenolides in the plant, but an industry-patented process now allows for removal of these irritants . Feverfew possesses antioxidant and anti-inflammatory properties; it is thought to inhibit proinflammatory mediators released from macrophages and to reduce neutrophil chemotaxis . Dermatologic applications include treatment of irritated sensitive skin, facial erythema, and tactile roughness.

Green Tea

The green tea plant ( Camellia sinensis ) has been cultivated in Asia for thousands of years. Green tea is made from unfermented tea leaves and can be ingested or applied topically. It contains the highest concentration of polyphenol antioxidants of any tea, save perhaps for white tea, which is the least processed of all teas. Eigallocatechin-3-gallate (EGCG) in green tea is the most potent of the polyphenols. Both topical and oral green tea can protect against inflammation, ultraviolet light-induced photodamage, chemical carcinogenesis, and photocarcinogenesis . Green tea has been studied as a treatment for both acne and photodamage .

Honey

Honey is a bee-derived substance composed primarily of fructose and glucose, but also contains numerous proteins, amino acids, vitamins, enzymes, and minerals. While honey is used to treat a wide variety of conditions including cutaneous infections and skin discoloration, it is most commonly applied to wounds to enhance healing. The latter effect is thought to be due to its antimicrobial properties and the enzymatic release of hydrogen peroxide. Active components of various honey formulations have been identified, e.g. methylglyoxal in manuka honey , and then associated with therapeutic benefits. Medical-grade honeys are now available by prescription, suggesting that honey may be entering the realm of conventional medicine. Although an allergic contact dermatitis to honey has been observed (probably related to propolis), there have been no reports of significant adverse events and topical application of honey is thought to be well tolerated .

Horse Chestnut Seed Extract

Oral horse chestnut seed extract (HCSE) ( Aesculus hippocastanum L.) is used to treat chronic venous insufficiency. In controlled studies, there was a decrease in leg volume, calf and ankle circumferences, and pain, with an efficacy equivalent to that of grade II compression stockings. HCSE contains escin (a triterpene saponin), which inhibits the release of elastase and hyaluronidase from leukocytes, thus preventing proteoglycan degradation and vascular leakage. Release of enzymes from activated leukocytes is considered one component of the pathophysiology of chronic venous insufficiency. Natural horse chestnut seeds are poisonous and need to be processed to remove esculin , a toxic component. Side effects of esculin include hepatotoxicity, renal toxicity, anaphylaxis, and possible potentiation of anticoagulation. Of note, drug interactions may limit the use of oral HCSE in patients receiving oral hypoglycemic agents, insulin, anticoagulants, aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), or other supplements that affect serum glucose levels .

Indigo Naturalis

Indigo naturalis is derived from the Strobilanthes formosanus plant and provides a well-known name for a dark blue color. Topical indigo naturalis has been observed to improve plaque psoriasis as well as nail psoriasis in children . The latter may be explained by an inhibition of epidermal keratinocyte proliferation by indirubin, the active component of indigo naturalis. Indirubin has been shown to down-regulate CDC25B expression, which is known to play an important role in the hyperproliferation of epidermal keratinocytes .

Licorice Root

Licorice root ( Glycyrrhiza inflata ; Glycyrrhiza glabra ) has long been considered a natural remedy. Glycyrrhiza glabra contains glabridin and Glycyrrhiza inflata contains licochalcone A, both of which have anti-irritant and anti-inflammatory properties . Licorice extract is produced by first boiling licorice root and then allowing the water to evaporate. It is used both topically and orally for rosacea and dermatitis and is typically found in preparations that target sensitive skin . Licorice also contains glycyrrhizin, a substance that, if ingested in high doses, can cause hypokalemia, arrhythmias, hypertension, and/or congestive heart failure.

Marigold

Marigold ( Calendula officinalis) is a flower native to northern Mediterranean countries. Topically, marigold is most commonly used to treat dermatitis, but has been employed for wounds, ulcers, thermal burns, and herpes zoster. There is also evidence to support the use of calendula ointment to reduce radiation-induced skin toxicity . Marigold contains flavonoids, triterpene saponins, and carotenoids which confer anti-inflammatory, antimicrobial, and immunomodulating properties. In animal studies, an increase in glycoproteins and collagen was observed in wound sites treated with topical marigold. There are rare reports of allergic contact dermatitis to Calendula , but it is generally well tolerated .

Menthol

Menthol is a naturally occurring plant compound that is used in multiple industries and products, including pharmaceuticals, pesticides, and flavoring agents. Topical preparations that contain menthol are used for their antipruritic, analgesic, and cooling properties. Menthol is thought to act through the cation channel TRPM8, a member of the TRP (transient receptor potential) family of ion channels, which is also activated by cold. However, the precise mechanism by which menthol suppresses pruritus is unclear. In addition to affecting sensory pathways, menthol exhibits antibacterial and antifungal activity .

Prebiotics and Probiotics

Prebiotics are non-digestible sugars that encourage the growth of certain desirable types of bacteria within the intestine. Probiotics are live microorganisms that are ingested in an attempt to alter the gastrointestinal flora into a more beneficial balance. Probiotics can be ingested in a tablet form or as a component of foodstuffs, especially yogurt, fermented and unfermented milk, miso, tempeh, and soy beverages. The most commonly used probiotics are Lactobacillus , Bifidobacterium , and Saccharomyces boulardii .

Patients with eczema have been shown to have abnormal gastrointestinal flora (e.g. a reduced proportion of Bifidobacteria spp. in the feces of infants with eczema) and they may have increased inflammation and permeability of their intestines. Probiotics decrease intestinal inflammation and permeability, and potentially may alter antigen presentation in a way that is beneficial to patients with eczema. However, the results of clinical trials have been mixed and outstanding questions remain, including the ideal patient, the type and dosage of the probiotics, and the timing and frequency of administration . Side effects usually consist of mild gastrointestinal symptoms, but there have been case reports of probiotic sepsis.

Tea Tree Oil

Tea tree oil is an essential oil from the leaves of the native Australian tree, Melaleuca alternifolia . The indigenous people of Australia use tea tree oil from crushed leaves as a traditional remedy for coughs and colds as well as to treat wounds and skin infections. Tea tree oil is commonly used as a topical antimicrobial agent and has shown efficacy in treating acne and cutaneous fungal and bacterial infections. There are multiple reports of the antiseptic properties of tea tree oil, thought in part to be due to disruption of bacterial membranes . Tea tree oil can be very irritating and is a cause of allergic contact dermatitis; it may also produce gynecomastia .

Turmeric

Turmeric is the ground root of Curcuma longa and its active compound is curcumin. Curcumin is the yellow pigment that gives turmeric, curry and yellow mustard their color, and it has been used for centuries in cooking and cosmetics. Turmeric has antimicrobial, antioxidant, anti-inflammatory, and anticancer activities . It inhibits lipoxygenase and cyclooxygenase, thereby reducing levels of leukotrienes, thromboxanes, and prostaglandins. Topical turmeric has been evaluated for psoriasis and wound healing , but color and odor limit its use.

Vitex

An extract of vitex dried fruit ( Vitex agnus-castus ) has been used to treat menstrual cycle disorders. As a corollary, oral vitex has also been used to improve hormonal acne in women. The extract is thought to be helpful in regulating ovulation and in reducing levels of luteinizing hormone, prolactin, fasting insulin and testosterone, thereby improving menstrual cycle-associated acne. Given the hormonal effects of oral vitex, it should not be used by pregnant or nursing women .