Blue vetch is a food which may result in allergy symptoms in sensitised individuals.

Blue Vetch Allergy Test: Allergen Exposure

Blue vetch is native to Eurasia, North America, temperate South America and East Africa, but its exact origins are unknown.

As a food crop, it is grown or collected for its drought-resistant, high-yielding, nitrogen-rich pulse which yields high-quality protein and carbohydrates. It is principally consumed in northern India and neighbouring countries, as well as in Ethiopia.

The immature seed can be eaten like green peas. The mature seed is eaten roasted or boiled, after soaking or parching, and the young shoots can also be cooked. The seed is often used in making dhal, paste balls for curry, or beverages. It can also be ground into a powder and mixed with wheat to make protein-enhanced bread.

A flour made from blue vetch seeds is used in cattle feeding and industrial processing in some countries.

The seeds have also been used in homeopathic medicine.

Due to the presence of a neurotoxin in blue vetch, consumption of large quantities for sustained periods can result in illness, and in some cases can cause irreversible paralysis.

Blue Vetch Allergy Test: Allergen Description

No allergens present in blue vetch have yet been characterised, however a number of potentially allergenic proteins have been identified.

Blue Vetch Allergy Test: 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.

Cross-reactivity and/or co-sensitivity have been reported among blue vetch, chickpea, and lentil.

Blue Vetch Allergy Test: Clinical Experience

Blue vetch as a dried legume is used in some regions of Spain in the form of flour for cooking and has been responsible for some cases of allergic reactions through food intake or contact.

Seventy-seven percent of patients in a Spanish study showed a positive skin test to blue vetch flour; 4 of these patients had developed clinical symptoms in relation to blue vetch, and 2 of them, in addition, to other legumes.

Two young women experienced symptoms after eating blue vetch. They reported previous hypersensitivity to other legumes.

Generalised urticaria and facial oedema in a 5-year-old, occurring a few minutes after ingestion, have been reported.

Occupational asthma has been reported following exposure to flour made from blue vetch, as well as to the closely related sweet pea.

A 42-year-old man was described who had worked as a carpenter for 6 years and who reported a history of rhinorrhoea, paroxysmal sneezing, naso-ocular pruritus, lacrimation, wheezing and dyspnoea attacks while preparing a mixture containing blue vetch flour.

Other reactions

Neurolathyrism is a neurological condition seen among people who eat the seeds of Lathyrus sativus as a principal source of food energy for 2 months or more. It is characterised by severe muscular rigidity and irreversible spastic paralysis of the lower limbs, spinal hyperreflexia, and structural changes of the skeleton and connective tissue.

The oil from the seeds is a powerful and dangerous cathartic that contains a poisonous principle, probably an acid salt of phytic acid.