f324 Hop

Allergens within Food of Plant Origin

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  • Latin name: Humulus lupulus
  • Family: Cannabaceae
  • Common names: Hops, Common Hops, European Hops
Food
A food, which may result in allergy symptoms in sensitised individuals.

Allergen Exposure

Geographical distribution
Native to Europe and western Asia, the Hop plant is now cultivated in North and South America, Africa, Asia and Australia. The plant is a perennial climber growing to 6m at a medium rate. “Hops” is the common term for either the dried flower heads as a whole or the extract, with a bitter taste and aromatic odour, from the dried pine cone-like fruit of the plant. Hops contribute flavour and aroma and act as a preservative in brewed alcoholic beverages, and are used medicinally. The extract may be in solid, liquid or oil form.
 
Environment
Hop grows in hedgerows, woodlands and sunny waste ground, as well as in cultivated fields, where it is trained on high trellises. The manufacture of beer utilises 98% of the world's production of Hops. Before the days of pasteurisation, brewers used Hops for their antibiotic properties as well as their flavour. In some countries the young shoots, heads, leaves and roots of the plant are eaten as vegetables. (The leaves contain rutin and if eaten raw should be very fresh.) A tea is made from the leaves and cones. Extracts from the plant, including the oil, are used as flavouring in non-alcoholic beverages, frozen dairy desserts, candy, baked goods, puddings and tobacco. The seeds contain gamma-linolenic acid, an essential fatty acid that is said to have many important functions in the human body and is rarely found in plant sources.
 
Hops are said to have various biological activities. (The antimicrobial activities are due to the bitter acids, especially lupulone and humulone, which give Hops their aroma and beer its bitter flavour.) Hops are widely used as a folk remedy to treat a wide range of complaints, including boils, cancer, cough, leprosy, tuberculosis, diarrhoea (including acute dysentery), toothache, jaundice, rheumatism, and worms. Hop flowers are popular as an infusion and can also be used to stuff pillows, so that the weight of the head will release the volatile oils.
 
Unexpected exposure
See under Environment. Also, a brown dye is obtained from the leaves and flower heads. An essential oil is used in perfumery. Extracts of the plant are used in Europe in skin creams and lotions for their alleged skin-softening properties.
 
Recently, counterculture entrepreneurs have apparently succeeded in grafting Hops tops onto marihuana plants and getting a "heady Hop". Conversely, they might have succeeded in getting a perennial marihuana by grafting the annual herb onto the perennial Hop.
 
Allergens
No allergens from this plant have yet been characterised.

Potential Cross-Reactivity

An extensive cross-reactivity among the different individual members of the family could be expected (1). Members of this family include Hemp (Cannabis sativa) and Japanese Hop (Humulus scandens). 

Clinical Experience

IgE-mediated reactions
Hops may uncommonly induce symptoms of food allergy or skin allergy in non-occupationally sensitised individuals. Occupational allergy may also commonly be associated with exposure to Hops (2). Hops have usually been picked by hand. (However, more recently, picking machines have been introduced in some countries.) Skin contact with the plant causes dermatitis in susceptible people. Hops dermatitis has long been recognised. In 14 Polish farmers complaining of work-related skin symptoms, these were caused most often by Hops (11%), followed by grain (5.6%), hay (5.5%) and straw (4.1%). Five farmers (6.8%) complained of hand dermatitis, 4 (5.5%) of airborne dermatitis, and 8 (11.0%) of pruritus. On skin prick tests, 5.5% of farmers reacted to grain dust, 5.5% to straw dust, 11% to hay dust, and 8.2% to Hops (3). Not only the hands and face, but legs may be involved due to Hop picking. Dislodged hairs from the plant can irritate the eyes.
 
Systemic and contact urticaria have been documented (4-5). A patient who presented 4 times with systemic urticaria associated with arthralgia and fever has been reported. Investigation confirmed allergy to Hops. The authors suggest that in some instances the adverse effects of Hops are not due to allergy but are a result of another mechanism which is unclear - the constituent lupuline may play a role (5).
 
The onset of occupational airborne dermatitis and hand dermatitis to Hops in a 57-years-old female farmer has been documented. The disease appeared at the age of 46, 30 years into working with Hops without any health problems. The patient had skin erythema of the face, neck and upper chest, oedema of the eyelids, and conjunctivitis, as well as acute dermatitis of the hands. Both fresh and dried Hops precipitated the symptoms. Onset occurred after half an hour of working and persisted over 1-2 days. Despite discontinuing work, the patient experienced several relapses of her dermatitis, and this was attributed to her use of a beauty cream and a herbal sedative, which both contained Hops extract. Sleeping in a bed with her husband, who worked with Hops, provoked relapses of the patient's dermatitis. (The husband sometimes felt too tired to wash thoroughly after working on the plantation.) (6).
 
Anaphylaxis following exposure to Hops has been reported (7).
 
Other reactions
Hop leaves contain lupin and rutin. Sometimes Hops are treated with sulphur dioxide to improve the colour and prevent change of active substances.
 
Hops contain a phytooestrogen. This phytoestrogen can also be detected in beer, but the levels are low and should not cause concern (8). In animal studies, approximately 500-fold greater levels were required for oestrogenic effects than can be found in any beer (9). The presence of 8-prenylnaringenin in Hops may provide an explanation for the accounts of menstrual disturbances in female Hops workers.
 
Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09
    2. Newmark FM. Hops allergy and terpene sensitivity: an occupational disease. Ann Allergy 1978;41(5):311-2
    3. Spiewak R, Gora A, Dutkiewicz J. Work-related skin symptoms and type I allergy among eastern-Polish farmers growing hops and other crops. Ann Agric Environ Med 2001;8(1):51-6
    4. Estrada JL, Gozalo F, Cecchini C, Casquete E. Contact urticaria from hops (Humulus lupulus) in a patient with previous urticaria-angioedema from peanut, chestnut and banana. Contact Dermatitis 2002;46(2):127
    5. Pradalier A, Campinos C, Trinh C. Systemic urticaria induced by hops. [French] Allerg Immunol (Paris) 2002;34(9):330-2
    6. Spiewak R, Dutkiewicz J. Occupational airborne and hand dermatitis to hop (Humulus lupulus) with non-occupational relapses. Ann Agric Environ Med 2002;9(2):249-52
    7. Stricker WE, Anorve-Lopez E, Reed CE. Food skin testing in patients with idiopathic anaphylaxis. J Allergy Clin Immunol;77(3):516-9
    8. Milligan SR, Kalita JC, Heyerick A, Rong H, De Cooman L, De Keukeleire D. Identification of a potent phytoestrogen in hops (Humulus lupulus L.) and beer. J Clin Endocrinol Metab 1999;84(6):2249-52
    9. Milligan S, Kalita J, Pocock V, Heyerick A, De Cooman L, Rong H, De Keukeleire D. Oestrogenic activity of the hop phyto-oestrogen, 8-prenylnaringenin. Reproduction 2002;123(2):235-42

2004



Further Reading