Conditions
Oral allergy syndrome
Understanding pollen-food (oral allergy) syndrome — why some raw fruits and vegetables trigger reactions in pollen-allergic children.
Cross Reactivity between Foods
If children are allergic to one food, they may also show reactivity to additional foods. This arises either because they are multiple food allergic (to unrelated foods) or because they are reacting to foods which belong to the same biological family. Seemingly unrelated foods may therefore contain the same allergen as another, e.g. peanut, tree nuts and sesame seeds. It should never be assumed that being allergic to one such food will cause clinical reactions to other related foods.
The most well-documented cross-reactivity is the one which occurs between apple and birch pollen. Nevertheless, all apple allergics are not necessarily allergic to birch pollen. The following are examples of claimed cross-reactivities based on studies with immunochemical methods and/or clinical diagnosis, some of these associations are stronger than others - the strong associations are bolded in black with highly relevant associations in red. The codes represent the Phadia codes for the allergy IgE test
Symptoms
Most people with OAS experience mild to moderate intra-oral symptoms, such as a 'metallic' taste, itching, burning and tingling. Occasionally, swelling of the lips, mouth, face, tongue and throat may occur. Symptoms are usually short-lived (a few minutes) and rarely progress to anything more serious. Occasionally, in highly sensitive individuals, gut pain, vomiting, diarrhoea and/or a flare in eczema may be experienced even when the food is eaten cooked. Symptoms are usually more severe during the season when the responsible pollen is at its height. The allergy specialist only rarely prescribes an injectable adrenaline device for use in the OAS.
Cross-reactions have been described for the following foods. Importantly not all the foods listed below will cause reactions for any one individual:
- Birch pollen (common in the UK), including hazelnut, apple, peach, pear, apricot, carrot, celery, cherry, chicory, coriander, fennel, fig, kiwifruit, nectarine, parsley, parsnip, pepper, plum, potato, prune, soy, wheat; Potential reaction: almond nut, and walnut.
- Alder pollen, including almond, apple, celery, cherry, hazel nut, peach, pear, parsley.
- Grass pollen (common in the UK), including fig, melon, tomato, orange.
- Mugwort pollen (more common in USA), including carrot, celery, coriander, fennel, parsley, pepper, sunflower.
- Ragweed pollen (common in the USA, and increasing in parts of Continental Europe), including banana, cantaloupe, cucumber, honey dew, watermelon, zucchini; Potential reaction: Dandelion or chamomile tea.
- Possible cross-reactions (to any of the above pollens), including berry (strawberry, blueberry, raspberry, etc), citrus (orange, lemon, etc), grape, mango, fig, peanut, pineapple, pomegranate, watermelon.
Treatment
- Awareness and diagnosis of OAS.
- Avoidance of the offending food, but only in extreme cases.
- Eating well-cooked, canned, pasteurized or frozen foods, as these cause little or no reaction.
- Peeling food has been shown to reduce the effects of the allergy in the throat and mouth, especially in the case of apples. These measures may not always help prevent/relieve symptoms in the gastrointestinal tract or skin for highly sensitive patients.
- Antihistamines may relieve the symptoms - especially during the pollen season.
- SLIT (Sub-lingual Allergy Immunotherapy) may improve OAS.
- Rarely, persons with severe reactions may consider carrying injectable medication, such as an EpiPen, to bring relief if necessary.