Plums – a blessing in autumn
Plums have been known in Poland since the 12th century. They are among the top 20 fruits with the highest production worldwide. Approximately 20% of plums are harvested from Prunus domestica, the domestic (European) plum tree, which belongs to the Rosaceae family. The name of this plant family is well known to allergologists, as discussed further below.
Poland is one of the five main plum producers in the European Union [2]. The ideal conditions for plum tree development are right here in our temperate climate. The fruit of this tree is harvested – depending on the species – from the beginning of summer until the end of autumn. The most popular plum in our country is the honeydew.
Plums have a high nutritional value – both fresh and dried. They are a valuable source of pectin, carotenoids, phenolic compounds and organic acids [1]. There are studies confirming that a high proportion of prunes in the diet is associated with:
- improved blood lipid profile,
- a reduction in bile acids,
- improved glucose and lipid metabolism,
- inhibition of osteoporosis development [1].
Prunes are great as a healthy snack. In the kitchen, they are also often used for baking cakes, frying jam and making traditional plum brandy [2]. They are ideal for drying. Consumer research shows that Poles most often buy dried plums at Christmas (67%) [2].
Allergies to plums – does it happen?
Plums, although so healthy, contain allergenic proteins. Their most significant allergen is Pru d 3, a protein belonging to the LTP group. Reactions to this very protein have been shown in more than 80% of people with plum hypersensitivity [3]. However, this type of allergy is extremely rare.
Usually, symptoms after eating prunes are not due to an allergy to the fruit itself, but to a cross-reaction. How does this reaction occur? The whole mechanism is based on homology, i.e. similarity between proteins. Lipid transfer proteins (LTPs) are allergens present in fruit, vegetables, nuts and cereals. They are also found in pollen-producing plants such as mugwort, plantain, olive, ragweed and cypress [4]. When the period of their intense pollenisation is underway (in the case of ragweed, it is September), eating a fruit that contains similar proteins (e.g. plums), in a person who is allergic to pollen, can cause complaints characteristic of allergy.
Stone fruits of the Rosaceae family, i.e. peach, apricot, cherry and plum, are the most implicated in such reactions, which are associated with LTP proteins [4,5]. It also happens that these fruits interbreed with each other, which means that the plum can cause symptoms in people with a peach allergy.
In addition, plums also harbour allergens from groups other than LTP. These include PR-10 proteins, which include Bet v 1 of birch pollen. PR-10 proteins are characterised by a very high degree of cross-reactivity and widespread occurrence in plants. Therefore, up to 70% of people allergic to birch can experience allergy symptoms after eating certain fruits (including plum) [4].
Allergy symptoms after prunes
Fruit, especially in its raw form, most commonly causes oral allergy syndrome (OAS) in people who are allergic to cross-contaminated pollen. This syndrome usually manifests itself within 2-15 minutes of contact between the fruit and the oral mucosa. It manifests itself by swelling, itching and/or numbness of the oral area (lips, tongue, palate). In very rare cases, it leads to systemic reactions (including anaphylactic reactions) [4].
Dried prunes, on the other hand, may contain large amounts of sulphites, which are preservatives with allergenic effects. In sensitised individuals, sulphites cause a range of complaints, including: urticaria, erythema and itching of the skin, nausea, vomiting, abdominal pain and even anaphylaxis.
