Route Of Exposure

Blackberry is native to Britain. It was always popular as a wild fruit and only developed as a garden fruit about 1850. The Blackberry is an evergreen or semi-evergreen plant with woody, scrambling stems. The ripe fruit is an aggregate of small, purplish-black droplets attached to a cone-shaped receptacle, which readily separates from the plant when the berries are ripe. Some 250 species of Blackberry are known. Blackberry is not a real berry but a conglomerate fruit much more closely related to Apple and Peach than to such true berries as Gooseberry, Blueberry and Tomato.

Blackberries can grow wild, mostly in hedgerows or meadows or on the edges of forests, but most commercially available Blackberries are cultivated. The fruit is eaten raw and in pastries, and is used in making syrups, jams and liqueurs. The root can be cooked, and a tea is made from the dried leaves. The young shoots are peeled and eaten in salads. Blackberries are a good source of vitamin C, fibre and folate.

The root bark and the leaves are strongly astringent, depurative, diuretic, tonic and vulnerary. They are used as a remedy for dysentery, diarrhoea, haemorrhoids, cystitis, etc. Externally, they are used as a gargle to treat sore throats, mouth ulcers, thrush and gum inflammations. Blackberry contains salicylates (natural aspirin) – but these may cause reactions in anyone intolerant to aspirin. Some people find that if they eat the fruit before it is very ripe and quite soft, it gives them stomach upsets.

Clinical Relevance

Allergen description

No allergens from this plant have yet been characterised.

Investigation of the serum of a 45-year-old man who developed systemic anaphylaxis after ingestion of Blackberry revealed IgE bands to Blackberry proteins of between 25 and 100 kDa, indicating that they were neither lipid transfer proteins nor proteins from the Bet v 1 family (both are low-molecular-weight proteins). However, a study reported that Blackberry may have a Mal d 1 homologues allergen (homologous to Bet v 1).

Potential Cross Reactivity

An extensive cross-reactivity among the different individual species of the Rosaceae family (Almond, Apple, Apricot, etc.), and more specifically the genus Rubus (Cloudberry, Dewberry, Raspberry), could be expected, but this has not been documented as yet

Clinical Experience

IgE-mediated reactions

Although hypersensitivity to the pollen and fruit of the Mulberry tree (Morus alba) has been reported, allergy to Blackberry has rarely been reported. This may be related to the general low allergenicity of this berry, the small amounts consumed or the restricted time frame of consumption. Low exposure to certain allergens might be the reason for the limited complaints recorded so far, but with the ongoing promotion for the consumption of small fruits, this situation might change.

Although anecdotal reports of allergy to Blackberry have been received, only 1 report has been published in the medical literature. Nonetheless, Blackberry may induce symptoms of food allergy in sensitised individuals, and suspicion of adverse symptoms to Blackberry should be entertained, in particular because of its frequent consumption and its allergenic potential. This fruit should be taken into consideration in the case of patients with a history of allergy to other fruits of the Rosaceae family, and in the case of pollen-sensitised patients with oral allergy syndrome.

A 45-year-old man is reported to have developed systemic anaphylaxis after the ingestion of Blackberries. He had experienced dyspnoea and pharyngeal and labial pruritus over the previous 25 years and clearly related these symptoms to the ingestion of Blackberries, Raspberries, Peanuts, certain brands of margarine, and fruity wines. However, symptoms of oral allergy syndrome were the most intense with Blackberry. In an episode 2 months prior to consultation, he had developed oral allergy syndrome accompanied by generalised urticaria, oedema of the glottis, dyspnoea, vomiting, diarrhoea and loss of consciousness after the ingestion of 2 Blackberries. SPT confirmed sensitisation to Blackberry. Skin reactivity was also found for Goosefoot/Lamb’s quarter (Chenopodium), Peanut, Wheat, Barley and Rye. An oral challenge test was not performed.

The same patient was included in a study of 4 patients with thrombosis associated with antiphospholipid syndrome, each of whom had experienced anaphylaxis attributable to ingestion of vegetables or fruit. The presence of IgE antibodies for a 45 kDa protein band in an Almond extract was detected in all 4 of these patients. No IgE antibodies specific for food panallergen lipid transfer proteins were detected.