Although hops have been used for brewing beer for over 1,000 years, their medicinal properties have also been valued from very early times. Hop pickers used to tire easily, apparently as a result of transferring some hop resin from their hands to their mouths, gaining hops a reputation as a safe sedative. Later, pillows filled with hops were used for insomnia and nervousness. Small bags of hops, wetted with alcohol and placed on the skin, were also said to reduce local inflammation.

Humulus [hops] and Cannabis are the only two genera in the family Cannabinaceae and there are many similarities between hemp (Cannabissativa) and the cultivated hop. The nettle family is also rather less closely related being in the same order, the Urticales. It is possible to produce viable grafts between hops and hemp and it is reported that pollination of hops by hemp, annual nettle (Urtica urens) or perennial nettle (Urtica dioica) stimulates cone development but only abortive embryos are produced. It was reported by Warmke and Davidson (1944) that hop scions grafted onto Cannabis stocks produced cannabinoid resins and this led to interest in the technique as a means of producing such material while avoiding legal restrictions.

Within the larger plant family, the only two relatives of Humulus are hemp (Cannabis) and nettles (Urticales), and the elm are all distant cousins. Before you ask, there are no "chemical" similarities between them. The resins produced by each are completely different.

Hops bring a lot more to beer than bitterness. The volatile oil, usually 0.5 - 3.0% (vol/wt) of hop cone, is an important part of many types of beer. Brewers seeking to maximize hop flavor and aroma generally make late kettle additions (0-15 min. before cooling) with high quality "aroma" hops. Dry hopping, i.e. the addition of hops to the secondary fermenter or serving tank, is another way to add hop character to a beer although the aroma components retained by this method differ from those obtained in late kettle additions.

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