- Theoretically, any food can induce an allergic response. However, only a limited number of foods are commonly involved in food allergic reactions.
- Some foods are associated most frequently with allergy in children (milk, eggs, cereals and peanuts) while others with allergy in adults (fish, shellfish, fruits, legumes - peanuts, soy, beans and peas - and nuts). This doesn’t mean that you cannot develop allergy to any kind of food at any age! The difference is given only by the fact that we are eating to different kind of foods at different ages.
- Both raw and cooked foods can cause allergy. Sometimes heating the allergenic food will destroy or reduce the number of allergens it bears (for example some of the milk allergens will be destroyed when boiling the milk). However this is not a general rule, as some foods can become more allergenic when they are exposed to heat through cooking. The most common example of this second situation are the peanuts which are mild allergens when raw but become highly allergenic through roasting. Other kind of food processing can also modify the allergenic potential of the food either to enhancing or to reducing it.
- Some people develop food allergy only after they have became sensitized to aeroallergens, particularly to pollens. Most frequently these people develop allergy to plant derived foods. The reason for this cross reaction is the fact that pollen contains substances which are also found in the fruits or other component of the plant. If allergy to pollen involves these substances then the body will react to them, both when inhaled (as pollen) or when ingested (as foods). Similarly, in some people food allergy can start manifesting only after patients have became allergic to house dust mites. However, this kind of cross-reactivity occurs less often than that between pollens and plant derived foods. If you are allergic to inhaled allergens and you also have symptoms like lip, tongue or throat itching or tingling, swelling, nettle rash or other symptoms suggestive of food allergy (for more details see the chapter food allergy) the table below might help you indentifying the food that causes these symptoms:
| Airborne allergen | Cross reactive food allergen |
| Birch pollen | Apple, kiwi, cherry, pear, peach, plum, banana, hazelnut, walnut, peanut, chestnut, soybean, celery, carrot, raw potatoes, tomato, bell pepper, avocado, chick pea, spinach, wheat, buckwheat, persimmon |
| Grass pollen | Raw tomato, melon, watermelon, orange, cherry, potato, wheat |
| Ragweed pollen | Watermelon, banana, chamomile, honey, sunflower seeds |
| Mugwort pollen | Celery, carrot, mustard, spices, melon, watermelon, apple, hazelnut, chestnut, chamomile |
| Japanese cedar pollen | Melon, apple, peach, kiwi |
| House dust mites | Shellfish, snails |
