Route Of Exposure

Cultivated in many parts of the world, this firm, medium-sized bean has a dark red skin and cream-coloured flesh. Its popularity can be attributed to its full-bodied flavour. There are many named varieties of the plant, ranging from dwarf forms about 30 cm tall to climbing forms up to 3 m tall.

The seeds of older Green bean pods are known as Red kidney beans, especially when they are dark red. White kidney beans, also referred to as Cannellini beans, do not have the robust flavour of the Red kidney bean.

Red kidney beans are the main ingredient of chilli con carne, and are also often served with rice. The mature seeds can be canned or dried. They can be boiled, baked, pureed, ground into a powder, or fermented. The seed can also be sprouted and used in salads or cooked. The roasted seeds have been used as a coffee substitute. The green pods may be used as a vegetable. The young leaves can be eaten raw or cooked as a potherb.

The green or dried mature pods, or the seeds alone, are reported to have laxative, diuretic, hypoglycaemic and hypotensive actions. Ground into flour, the seeds are used externally in the treatment of ulcers. The seeds or whole plant may be used as a homeopathic remedy for a variety of diseases.

Haemagglutinin, a lectin, occurs naturally in the Red kidney bean. It is inactivated by thorough cooking of well soaked beans.

Clinical Relevance

Allergen decription

No allergens from this plant have yet been characterised. An alpha-amylase inhibitor has been detected. The allergenicity of this protein is unknown.

Potential Cross Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected but in fact is not seen frequently. In an in vitro study, the specific IgE binding by protein extracts of 11 food legumes was examined by IgE antibody determination and RAST inhibition. Cross-allergenicity was demonstrated to be most marked among the extracts of Peanut, Garden pea, Chick pea, and Soybean. However, clinical studies have found that there is little cross-reactivity among members of the Fabaceae (Leguminosae).

A study investigated the in vitro cross-reactivity of allergens from Mesquite tree pollen (Honey locust tree; Prosopis juliflora) and Lima bean (Phaseolus limensis/Phaseolus lunatus). Of 110 patients with asthma, rhinitis or both, found through intradermal skin determination to be evaluated, 20 were highly positive to Mesquite pollen extract. Of these, 12 patients showed elevated level of IgE antibodies to Mesquite pollen extract alone, and 4 to both Lima bean and pollen extract. Lima bean extract could inhibit IgE binding to Mesquite in a dose-dependent manner. Also, humoral and cellular cross-reactivity was demonstrated. Although cross-reactivity was not investigated between Mesquite and Red kidney bean per se, cross-reactivity may exist between pollen from this tree and other species of Phaseolus.

Clinical Experience

IgE-mediated reactions

Red kidney bean does not commonly induce symptoms of food allergy in sensitised individuals, but as with other legumes, allergic reactions are possible.

A study reports on a 33-year-old woman who developed tongue swelling and burning and mouth itching minutes after eating baked Beans. Similar symptoms occurred a day after ingesting Pea soup, and on another occasion within 15 minutes of eating a Bean burrito, and again 20 minutes after eating chilli containing Kidney and Pinto beans. SPT was positive to Red kidney and White bean but negative to Pea, Green and Lima bean. IgE antibodies were detected to Red kidney, White, and Pinto bean, and to Chick pea, Pea and Black-eyed pea.

Hand eczema was investigated among 50 caterers and found to be a result of occupation in 47 and endogenous in 3 cases. Contact dermatitis to Red kidney bean, along with skin reactivity, was found in 1 of former group.

Other reactions

Red kidney beans contain haemag-glutinating lectins, which are toxic. Between 1976 and 1989, 50 incidents of suspected Red kidney bean poisoning were reported in the UK. Of these patients, 9 reported the onset of nausea, vomiting and diarrhoea within 1-7 hours of ingestion. The diagnosis was confirmed by the detection of haemagglutinin in the Beans. The diagnosis was made in a further 23 incidents on the basis of symptoms, incubation time and the preparation of beans prior to consumption. In many of the outbreaks reported, the implicated Beans were consumed raw or following an inadequate heating process.

The root is dangerously narcotic. Large quantities of the raw mature seed are poisonous. This Bean is a notorious source of flatulence.

Occupational contact dermatitis caused by leaves of the Phaseolus plant was reported in a 41-year-old male farmer. Skin lesions appeared soon after he started work on the farm. His main activity was cultivation of Sugar beet, Kidney beans, cereals, Potatoes and Rape. Initially, there were inflamed, scaly patches disseminated over the body. Several years later, a chronic hand eczema appeared. The skin lesions on the body showed a seasonal pattern, with aggravations starting in spring, reaching maximum intensity in summer, and gradually fading in the autumn after the end of field work on the farm. Field work and threshing pods of the Red kidney bean plant in order to recover Kidney beans were activities particularly associated with his skin problems. Approximately 2 to 3 hours after the start of these activities, pruritus appeared, and several hours later erythema of exposed skin appeared, followed by eczema and vesicles. While threshing Phaseolus pods, the patient also experienced dyspnoea. SPT with the leaf was negative, but positive with patch tests.