Popularly known as echinacea, there are three species of this plant in use as therapeutic supplement. These species include; Echinacea pallida, Echinacea purpurea, and Echinacea angustifolia. All three are native North American plants and have a rich history of use by the Great Plains Indian tribes.  The use of echinacea as a medicinal herb was passed on to early white settlers. Soon After, echinacea angustifolia and pallida were included as official medicines in the United States National Formulary until 1950.  The use of echinacea declined with the rise of antibiotics in the United States; however it has seen continual use in Europe.
The relatively recent advent of antibiotic resistance has led to a resurgence in the use of echinacea; increasing its popularity as an effective botanical medicine. As one of the first herbal medicines to be ‘rediscovered’ in the late 1980’s and early 90’s, many echinacea products were impure and adulterated with other similar, but less effective herbs. Because of this discrepancy, clinical studies conducted on echinacea dating prior to 1991 (when the adoption of stricter standardization regulations for this herb began) may be considered unreliable. 
Historical use of echinacea involved treatments of many different infectious processes, allergic disease, rheumatism, and even rattlesnake bites. As a treatment for skin irritations, echinacea was also widely used on boils, abscesses, skin ulcers, eczema, psoriasis and bee stings.
The roots, leaves, and flowers of echinacea are used as medicine. Typically, echinacea is standardized according to one of its main constituents, echinacoside. The majority of echinacea’s primary/active constituents of have not yet been identified, however. As mentioned previously, many earlier echinacea products were adulterated. Despite the increasingly available means used to identify echinacea species, some products continue to be mislabled. 
Modern clinical investigations have elucidated specific uses for echinacea; many of these conditions are somewhat similar to its historic applications. Despite these findings, other studies have revealed antagonistic results as to the efficacy of echinacea. One of the main uses of echinacea is for upper respiratory tract infections (i.e. colds and influenza). Echinacea has been shown to exhibit certain antiviral and immune system modulatory effects. More specifically, echinacea can increase the activity of white blood cells by increasing the release of tumor necrosis factor (TNF), interleukin-1 (IL-1), and interferon. There are several different constituents of echinacea that are responsible for these effects. [5, 6]
Some research regarding Echinacea’s effects on cold symptoms suggests that it is effective due to its purported anti-inflammatory effect. Furthermore, evidence suggests that it may inhibit the cyclooxygenase and 5-lipoxygenase enzyme pathways -the two main inflammatory pathways in the body. [7, 8]
In the area of wound and tissue repair, echinacea appears to stimulate the production of tissue precursors and anti-inflammatory hormones found within the body (e.g. cortisol).  Other echinacea constituents may prevent bacteria-induced breakdown of infected tissue and promote tissue healing. Research also points to the ability of echinacea to assist the skin in recovering from ultraviolet radiation damage, or as it is most commonly referred to as, sun burn. 
Echinacea is also useful in treating fungal infections. Some of echinacea’s known constituents have been shown to have antifungal activity and may be effective against the main cause of yeast infections, Candida albicans. 
Overall, echinacea is an excellent antibacterial, antiviral, and antifungal herb with wide-reaching application. Benefits can be obtained from taking echinacea either acutely, or over an extended period of time, for immune enhancement. For example, persons often supplement with echinacea over a period of weeks to garner protection against winter illness.
Contrary to popular belief, echinacea can be taken for periods longer than eight weeks without risk of decreased immunostimulatory efficacy of the herb. This information was propagated based on flawed analysis of several studies in which patients took the herb. There is no evidence to back this claim. 
Multiple dosing recommendations have been made based on various clinical studies. Tablets may be taken (each one containing roughly 6.78 milligrams crude herb) in sets of two, three times a day, for the duration of symptoms.  Freeze dried extract is available in capsules; dosages for this form of echinacea have been set at 100 milligrams, taken three times per day.  The tincture extract form of the herb may be taken as often as needed; usually equaling 20 drops, administered every 2-3 hours. These dosages are then reduced to three times daily for the duration of symptoms. 
Echinacea Side Effects:
Echinacea is usually well tolerated by the majority of people that wish to supplement with this herb.  There have been some reported side effects, including nausea, fever, vomiting, heartburn, unpleasant taste, dry mouth, headache, and a tingling and numbness of the tongue.  Allergic reactions are also of concern with echinacea. These, like other side effects, are highly uncommon. However, some individuals with underlying medical conditions (i.e. those with atopic disease, allergy, eczema, and asthma) appear to be more sensitive to echinacea than healthy individuals. 
Additionally, people that are allergic to the Asteraceae/Compositae family of plants (ragweed, chrysanthemums, marigolds, daisies, and others) may be more susceptible to echinacea allergy.  Research has shown that large doses of echinacea therapy do not seem to induce any toxic or carcinogenic processes. 
Echinacea General Interactions:
There are no known interactions with other herbs or supplements, foods, or lab tests.
Echinacea Drug Interactions:
There are no specific drug interactions known, however echinacea may increase the availability of certain drugs in the body by down regulating the liver enzymes that typically dismantle them.  If prescription medications are taken while supplementing with echinacea, one should be monitored for side effects, as echinacea has been shown to increase the availability of drugs within the system.
Taking echinacea with immunosuppressive drugs contraindicated (largely on a theoretical basis). Because of Echinacea’s immune-stimulating properties, it should not be taken by people on immunosuppressive drug regimens, include high dose corticosteroids.
Echinacea Disease Conditions:
As previously stated, people with allergies, asthma, or eczema may be more susceptible to echinacea allergy. In total, there are 23 reports of allergic reactions from taking echinacea, in which 34% of subjects had atopic disease. 
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