Spinach
Summary
Spinach is a nutritious, leafy vegetable consumed worldwide. The leaves can be consumed raw or cooked, and can also be dried to form a powder used as a natural food dye. Clinical reports of spinach allergy are rare. Case reports of single patients have shown that allergic reactions can occur through spinach ingestion of cooked or raw leaves, and inhalation. In the small number of cases reported, reaction to spinach ingestion appear to be similar to those of oral allergy syndrome. Cross-reactivity of spinach allergens have been linked to mushroom, tomato, mold and latex.
Route Of Exposure
Main
The leaves can be consumed either raw or boiled and consist of three varieties: Savoy (wrinkled-leaf), smooth (flat leaf) and a hybrid, semi-savoy (semi-wrinkled leaf).
Other topics
Dried spinach powder can be used as a natural green coloring in foods such as pasta, and this powder can be inhaled.
Clinical Relevance
Although spinach contains histamine (37.5 mg/dl), which can cause pseudoallergic reactions, reports of spinach allergy either by ingestion or inhalation are rare. This may be due to the rapid denaturation of the principal allergens during digestion. However, in a prospective study of 80 Indian children aged 2–14 years with wheezing or physician-diagnosed asthma, spinach was shown to be the most common sensitive food allergen out of the 13 food allergens examined by skin prick test, where 25 % of children showed skin reactions.
In a UK prospective study assessing systemic reactions during skin prick testing between 2007-2013, of approximately 31,000 who underwent skin prick testing only 24 patients had systemic reactions, where 1 of these was an asthma patient having a mild systemic reaction to spinach.
Other reports of sensitization to spinach are limited to individual case reports: A 48 year-old woman with a positive skin prick test to spinach showed signs of oral allergy syndrome after spinach ingestion. A 23-year-old, nonatopic woman presented with severe angioedema of the lips and tongue after ingestion of spinach leaves. The acute reaction was suspected to be IgE-mediated as the patient had positive skin prick tests and in vitro blood tests to spinach (and tomato). History revealed previous episodes of urticaria and angioedema after the ingestion of raw and cooked spinach and tomato, and rubisco was determined as the culprit allergen. One case of asthma induced by inhalation of dried spinach powder was reported in a 30-year-old male pasta factory technician, who had a positive skin prick test and positive in vitro blood test to spinach extract.
Cross-Reactivity
Alternaria-spinach syndrome involves cross-reactivity from the mold Alternaria alternata and its major allergen Alt a 1, with allergens from spinach (and mushroom Agaricus bisporus). Cross-reactivity of a 30 kDa protein, suspected to be the Alt a 1 allergen was present in spinach extract. In addition to Alternaria alternata, a 30 kDa spinach protein showed cross reactivity to the molds Cladosporium herbarum and/or Aspergillus fumigatus in seven mold-allergic patients. There have also been single reports of cross reactivity to tomato (Solanum lycopersicum) and mushroom (Agaricus bisporus), as well as one report of exercise-induced anaphylaxis with a cross-reaction to latex.
References
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