Cranberry is a very small, prostrate, evergreen shrub, growing wild in northern Europe and in the northern regions of North America, but now also extensively cultivated in Russia and North America. This helps to compensate for the extensive loss of the berry’s natural habitat of large sandy bogs.

The stem is very slender, vinelike and creeping, and the leaves are small (less than 1.2 cm), leathery and lance-shaped. The small flowers are pink to red and appear in June. The bright red, round berries are about the size of currants (about 6 mm) and have an acid taste. They ripen in September and often persist through the winter.

The varieties may be confused, especially as Small cranberry (Vaccinium microcarpum) and Bigger cranberry (Vaccinium oxycoccos L.,) are popular berries in Nordic countries and Russia. The American cranberry (V. macrocarpon) is very similar to V. oxycoccus and is sometimes regarded as the same species. Other fruits in the genus Vaccinium are erroneously called cranberries; V. vitis-idaea (cowberry, foxberry, mountain cranberry, rock cranberry, lingonberry) is not cultivated but gathered and is used in Europe, and especially in Scandinavia, in food products such as preserves and beverages. The highbush cranberry, Viburnum opulus, belongs to the family Caprifoliaceae.

Cranberry is commonly too bitter to be eaten fresh but may be sweetened and preserved as sauce, chutney, jelly or pastry filling, or bottled as juice. Cranberry juice ‘cocktail’, with other juices used for sweetening, is a popular commercial product in the US. In the United States and Canada, cranberries are traditionally associated with Thanksgiving and Christmas meals. The fruit is even used to make gravy. Canned whole cranberries and cranberry sauce and jelly are commercially available, as are frozen cranberries. Dried cranberries can be used like raisins in baked goods or as snacks. A tea is made from the leaves.

Native Americans used the berries, twigs, and bark for medicinal purposes. An infusion of the plant has been used to treat cases of slight nausea.

In recent years, cranberry products have been increasingly marketed as a natural remedy for recurrent urinary infections. Cranberry appears to inhibit the attachment of pathogens to uroepithelium and may decrease the number of symptomatic urinary tract infections. (1, 2). The juice of the fruit is used to clean silver. A red dye is obtained from the fruit.

IgE-mediated reactions

Only one report of clinical allergy to cranberry has been documented to date. (3) 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 of the consumption of small fruits, this situation might change. (4)

Food-dependent exercise-induced anaphylaxis (FDEIA) to cranberry was described, where anaphylactic symptoms appeared not only after postprandial exercise, but also when the food allergen was ingested immediately after prolonged exercise. The patient, a 27-year-old female, reported having experienced five incidents of FDEIA in the previous 12 years following ingestion of different fruits: plums, grapes, cranberries, peaches, blackberries and raspberries. In some episodes the fruits were eaten together; therefore, the precise identification of the culprit food was uncertain. The patient experienced two typical episodes of FDEIA. The first had occurred 12 years previously, after 30 minutes of intensive walking, preceded by eating blackberries. Symptoms included generalised urticaria, facial angioedema, nausea, vomiting and weakness. The second was precipitated 10 years previously by ingestion of raspberries, and prolonged physical exercise started about 3 hours later. After 1 hour of dancing the patient developed anaphylactic symptoms which involved disseminated urticaria accompanied by facial angioedema and nausea. A particular episode followed strenuous and prolonged exercise, when she ate her first meal that day (potato, chicken and cranberry). About 10 minutes later, urticaria localised on the neck and hands developed, which was partially reduced by cetirizine. Four hours later, soon after ingesting white grapes, and shortly thereafter dancing intensively, she developed anaphylaxis. Skin-prick tests were positive for peach, raspberry, cranberry, nectarine, blackberry and black grape. Total serum IgE was 119 kU/L. An exercise challenge after ingestion of foods was not performed. (5)

In a report from the USA of a review of 601 patients (aged from 1 to 79 years) who experienced anaphylaxis, causes of anaphylaxis were elucidated in 41% of cases. Known causes included foods in 131 patients (22%), medications in 69 cases (11%), exercise in 31 cases (5%), and latex in 6 (1%). Of the 133 food reactions, shellfish was responsible in 45, peanuts in 25, food additives or spices in 15, tree nuts in 13, beef in 8, almonds or peaches in 5, pork in 4, cashews in 4, eggs in 3, and in one for the following foods: tuna, banana, cranberry, milk, kiwi, wheat, Cheetos, orange, apples, sesame seeds and fish. (6)

Nonetheless, judging from reports of adverse effects from other berries, and especially other family members, cranberry may induce symptoms of food allergy in sensitised individuals.

For example, a 25-year-old woman reported adverse reactions to the close family member lingonberry (V. vitis-idaea). While eating lingonberry jam, she developed itching wheals around her mouth. Symptoms resolved spontaneously. During a second episode, when she again ingested a very small amount of lingonberry jam several days later, she immediately noticed more intense symptoms, including intense itching on her mouth, tongue and throat, and wheals over her mouth. Symptoms resolved spontaneously within an hour. Skin-specific IgE testing using a prick-prick method with fresh lingonberry was positive. (2)

Therefore, as cranberry is frequently and increasingly being consumed, suspicion of adverse symptoms to cranberry should be entertained.

Other reactions

High intake of cranberry juice may result in interaction with the drug warfarin, which can potentiate bleeding. (5) A previous study demonstrated that ingestion of 250 ml of cranberry juice 3 times a day for 2 weeks was associated with a marked increase of salicyluric and salicylic acids in urine within 1 week of the start of the intervention. After 2 weeks, there was also a small but significant increase in salicylic acid in plasma. (7) The presence of salicylic acid in cranberry was proposed as responsible for fatal bleeding in a patient on warfarin who ingested cranberry juice. (8)

No allergens from this plant have yet been characterised.

Homologues to Mal d 1 and Mal d 3 – could be detected in genomic DNA from cranberry; the respective genes were yet to be cloned. (4) However, the potential allergenicity of the recombinant gene products had not been defined.

A report was made about the closely related family member cowberry (lingonberry; V. vitis-idaea). A patient experienced intense itching on her mouth, tongue and throat, and wheals over her mouth, after eating lingonberry jam. Serum-specific IgE was detected to medium- and high-molecular-weight proteins, indicating that they were probably neither lipid transfer proteins nor proteins from the Bet v 1 family, which are both low-molecular-weight proteins. (2)

Cross Reactivity

There is potential cross-reactivity with other fruits in the genus Vaccinium that are erroneously called cranberries, (9) such as V. vitis-idaea (cowberry, foxberry, mountain cranberry, rock cranberry, and lingonberry).

Last reviewed : June 2022