Why can cucumbers be bitter?
Cucumbers belong to the cucurbitaceae family (just like pumpkins, watermelons, melons, courgettes). They have been cultivated all over the world – under various environmental conditions – for 3,000 years. Cucurbits are linked to the origins of agriculture. Cucumbers arrived in Europe from India. They first made their way to Greece and Italy, then (in the 9th century) to France and (in the 14th century) to England [1].
What is characteristic of the cucurbitaceous family is its content of cucurbitacin, an amino acid that has protective properties. It has a repellent effect on most insect species – with the exception of the cucumber beetle. It is due to kucurbitacin that fresh cucumber and pumpkin seed oil have a bitter aftertaste [1]. Most of the bitterness is under the dark green part of the skin. Some cucumber varieties show an increased susceptibility to bitterness, caused, for example, by a sudden change in weather conditions (drought, temporary cooling) [2].
Cucumber allergy vs. occupational allergy
Cucumber allergy is mainly described in the context of health problems in greenhouse workers. People doing such work have to reckon with exposure to high concentrations of allergens in enclosed spaces. Sources of these allergens include not only cultivated vegetables, but also flowers, insects and even mites (some of which live on plants). Sensitisation to cucumbers (resulting in allergic rhinitis, occupational asthma or contact urticaria) has been confirmed, for example, in a group of people who, after working in a greenhouse for 1-3 years, began to experience symptoms such as:
- sneezing
- runny nose
- itching and swelling of the skin.
Some of them, despite the onset of symptoms, continued to work, as a result of which the complaints evolved into coughing and shortness of breath [3].
Cucumber allergy or cross-reaction?
Mostly, however, it is not cucumbers that are the primary source of sensitisation. Symptoms following their consumption can occur as a result of cross-reactions. These vegetables have profilins in their protein composition – molecules that are ubiquitous in pollen and foods of plant origin. Sometimes, the body takes these as allergens regardless of the source. Therefore, an allergic reaction to cucumbers is not uncommon in people who are allergic to pollen. Cucumbers (along with kiwi, melon, watermelon, banana and apricot) are on the list of foods that most commonly cause oral allergy syndrome (OAS) in people with grass allergy [4]. It is not without significance here that the peak pollen season for grasses coincides with the harvest season for these vegetables.
Cross-reactions after eating cucumbers may also accompany ragweed and latex allergy [5,6]. A rare case of an anaphylactic reaction in a woman who ate cucumbers and ended up in the emergency room 5 minutes later with dizziness, vomiting, shortness of breath, erythema on the chest and itching of the mucous membranes has been linked to latex hypersensitivity [6].
