Typically, the sensitivity is to proteins in the white, rather than the yolk.Milk from cows, goats, or sheep is another common food allergen, and many affected people are also unable to tolerate dairy products such as cheese. A small portion of children with a milk allergy, roughly 10%, have a reaction to beef because it contains small amounts of protein that are also present in cows milk.Seafood is one of the most common sources of food allergens; people may be allergic to proteins found in fish or to different proteins found in shellfish (crustaceans and mollusks).Other foods containing allergenic proteins include soy and wheat, and to a lesser frequency, fruits, vegetables, maize, spices, synthetic and natural colors, and chemical additives.Balsam of Peru, which is in various foods, is in the "top five" allergens most commonly causing patch test reactions in people referred to dermatology clinics. Other than oral ingestion
Sensitization can occur through the gastrointestinal tract, respiratory tract and possibly the skin. Damage to the skin in conditions such as eczema has been proposed as a risk factor for sensitization.While the most obvious route for an allergic exposure is oral ingestion, some reactions are possible through external exposure. Peanut allergies are much more common in adults who had oozing and crusted skin rashes as infants. Airborne particles in a farm- or factory-scale peanut shelling or crushing environment, or from cooking, can produce respiratory effects in exposed allergic individuals.
Does the amino acid sequence of the transferred proteins resemble the sequence of known allergenic proteins? Are the transferred proteins resistant to digestion - a trait shared by many allergenic proteins? Genes approved for animal use can be restricted from human consumption due to potential for allergic reactions. In 1998 Starlink brand corn restricted to animals was detected in the human food supply, leading to first a voluntary and then a FDA mandated recall. There are requirements in some countries and recommendations in others that all foods containing GMO ingredients be so labeled, and that there be a post-launch monitoring system to report adverse effects (much there exists in some countries for drug and dietary supplement reporting). Restaurants
In the US, the FDA Food Code states that the person in charge in restaurants should have knowledge about major food allergens, cross-contacts, and symptoms of food allergy
reactions. Restaurant staff, including wait staff and kitchen staff, may not be adequately informed about allergenic ingredients, or the risk of cross-contact when kitchen utensils used to prepare food may have been in previous contact with an allergenic food. The problem may be compounded when customers have a hard time describing their food allergies or when wait staff have a hard time understanding those with food allergies when taking an order. Diagnosing issues
There exists both over-reporting and under-reporting of the prevalence of food allergies.