Funny, the reason I've come back onto BW today was to see about exactly this! My DS does also seem to be reacting to apples although I am not sure I would consider it (yet) to be an allergy.
I never used to be able to eat apples - they always gave me a stomach ache. Peeled wasn't as bad, tolerable, but still some discomfort. Any apples processed or cooked were fine.
When I got pregnant my cravings for crunchy juicy foods led me to an apple one day and I was FINE - and ate them throughout my pregnancy.
Introduced apples to DS about a week-ish ago, at breakfast. After three days of his morning naps being cut short and him seeming to be in some discomfort I put it together and realised that it could be the apples. Stopped with apples, he started sleeping again! Went back through my notes and realised it was the same on "pear days." Interestingly, after two or three days of pears he started refusing them. I have tried a few times to give them to him again and he won't eat them.
I've just checked up on this and it seems that an allergy to apples (amongst other things) can be a sign of a pollen allergy. There are also cross reactions.
Anyone, or anyone's LO have reactions that fit one of these:
Allergies to a certain pollen are associated with OAS reactions to certain foods. For instance, an allergy to ragweed is associated with OAS reactions to banana, watermelon, cantaloupe, honeydew, zucchini, and cucumber. This does not mean that all sufferers of an allergy to ragweed will experience adverse effects from all or even any of these foods. Reactions may begin with one type of food and with reactions to others developing later. However, it should be noted that reaction to one or more foods in any given category does not necessarily mean a person is allergic to all foods in that group. Often well-cooked, canned, pasteurized or frozen food offenders cause little to no reaction due to denaturation of the cross-reacting proteins.[2]
* Alder pollen: almonds, apples, celery, cherries, hazel nuts, peaches, pears, parsley
* Birch pollen: almonds, apples, apricots, avocados, carrots, celery, cherries, chicory,[4] coriander, fennel, fig,[5] hazelnuts, kiwifruit, nectarines, parsley, parsnips, peaches, pears, peppers, plums, potatoes, prunes, soy, strawberries, wheat; Potential: walnuts
* Grass pollen: fig,[5] melons, tomatoes, oranges
* Mugwort pollen : carrots, celery, coriander, fennel, parsley, peppers, sunflower
* Ragweed pollen : banana, cantaloupe, cucumber, honey dew, watermelon, zucchini; Potential: Dandelions or chamomile tea
* Possible cross-reactions (to any of the above): berries (strawberries, blueberries, raspberries, etc), citrus (oranges, lemons, etc), grapes, mango, figs, peanut, pineapple, pomegranates, watermelon
from
http://en.wikipedia.org/wiki/Oral_allergy_syndrome