Tanacetum parthenium

Tanacetum parthenium, known as feverfew, is a flowering plant in the daisy family, Asteraceae. It may be grown as an ornament, and may be identified by its synonyms, Chrysanthemum parthenium and Pyrethrum parthenium. It is also used as a herbal medicine in the traditional sense and a dietary supplement to treat headache and other ailments, as well more recently in topical skin care as an antioxidant.

Description
The plant is a herbaceous perennial that grows into a small bush, up to 70 cm high, with pungently-scented leaves. The leaves are light yellowish green, variously pinnatifid. The conspicuous daisy-like flowers are up to 20 mm across, borne in lax corymbs. The outer, ray florets have white ligules and the inner, disc florets are yellow and tubular. It spreads rapidly by seed, and will cover a wide area after a few years. The plant produces achene fruit, and grows in stony slopes and river beds.

Location and cultivation
Feverfew is native to Eurasia, specifically the Balkan Peninsula, Anatolia, and the Caucasus, but cultivation has spread it around the world and the rest of Europe, North America, and Chile.

A perennial herb, it should be planted in full sun, 38 to(-) apart, and cut back to the ground in the autumn. It grows up to 70 cm tall. It is hardy to USDA zone 5 (−30 °C). Outside of its native range, it may become an invasive weed.

Traditional medicine
In traditional medicine, feverfew has been used to treat headache, but there is no confirmed scientific evidence that it has such an effect. Feverfew contains parthenolide, which is under basic research to assess its properties on cancer. Feverfew is registered as a traditional herbal medicine in the Nordic countries under the brand name Glitinum. Only powdered feverfew is approved in the European Union herbal monograph.

Dietary supplement
The parthenolide content of commercially available feverfew supplements varies substantially (by more than 40-fold) despite labeling claims of "standardization".

Topical skin care
In topical skin care, bioactive compounds derived from the feverfew plant are used for their antioxidant and anti-inflammatory properties. These bioactives are obtained through processing the aerial parts of the feverfew plant—specifically the flowers, leaves, and stem—when the plant is in full bloom, utilizing methods such as grinding, maceration, and pressing. This process yield an extract, separated from the plant's fibrous material.

Research in vivo has identified four primary compounds mostly responsible for feverfew's effects: camphor, parthenolide, luteolin, and apigenin. Camphor stands out for its aromatic nature, while luteolin and apigenin are classified as flavonoids. However, due to their less favorable cosmetic profile, camphor, luteolin and apigenin, might be omitted from cosmetic formulations.

A systematic review focusing on the consumption of feverfew liquid extract, specifically formulations containing a minimum of 0.2% parthenolide, has validated its anti-inflammatory activity, capacity to inhibit histamine release, and potential as a chemotherapeutic agent through the suppression of microbial growth and cytotoxicity linked to the disruption of DNA replication. Nonetheless, given parthenolide's significant potential as a skin sensitizer, its application in topical treatments is deemed unfeasible.

Further research explored the use of parthenolide-depleted feverfew extract in vitro (PD-feverfew) to mitigate the risk of allergic reactions and contact dermatitis associated with parthenolide. This investigation, which involved 1,200 participants, demonstrated clinical tolerance and affirmed that the removal of parthenolide does not compromise the extract's antioxidant efficacy. The findings indicate that PD-feverfew reduced smoke- and UV-induced DNA damage, cellular apoptosis and inflammation.

Adverse effects
Long-term use of feverfew followed by abrupt discontinuation may induce a withdrawal syndrome featuring rebound headaches and muscle and joint pains. Feverfew may cause allergic reactions in those allergic to the daisy family, including contact dermatitis or swelling and numbness of the mouth. Other side effects have included gastrointestinal upset such as mild nausea, vomiting, abdominal pain, diarrhea, and flatulence, which are, fortunately mild and transient. When the herb is chewed or taken orally it may cause mouth ulcers. Feverfew should not be taken by pregnant women. It may interact with blood thinners and increase the risk of bleeding, and also may interact with a variety of medications metabolized by the liver.

History and etymology
The word feverfew derives from the Latin word febrifugia, meaning 'fever reducer', although it no longer is considered useful for that purpose.

Although its earliest medicinal use is unknown, it was documented in the 1st century CE as an anti-inflammatory by the Greek herbalist physician Dioscorides.