[Bird-egg syndrome in children]

Allergy to egg is highly frequent in childhood. In general, children allergic to egg react principally to the ingestion of egg white. Egg yolk contains various proteins but the major allergens are contained in egg white. The principal allergens are ovalbumin, ovomucoid, ovotransferrin, and lysozyme. These proteins have been sequenced. In some cases, a relationship between type I hypersensitivity with respiratory symptoms due to bird antigens and allergy to egg yolk has been described. This association is known as bird-egg syndrome, which is caused by sensitization to chicken serum albumin (alpha -livetin) and is characterized by the development of respiratory and gastrointestinal symptoms after egg intake or after contact with bird antigens. The initial symptoms are usually asthma with or without rhinoconjunctivitis due to contact with birds. Individuals first become sensitized to bird proteins (feathers, excrement, serum and meat) and subsequently develop egg allergy. Although bird-egg syndrome has been described principally in adults, especially in women, it can also affect children in whom the syndrome presents certain differentiating characteristics in relation to the more common sensitization to egg white. Gastrointestinal and respiratory symptoms are more common than cutaneous symptoms and sensitization to egg yolk is more frequent than that to egg white. In children with allergy to birds and egg, egg allergy is usually more persistent; tolerance is not always achieved and develops later. Sensitization to other aeroallergens is also greater in individuals with allergy to birds and egg. Sensitization to egg sometimes precedes respiratory sensitization to bird proteins, a process known as bird-egg syndrome. By way of example, the case of a child who clinically presented bird-egg syndrome is presented at the end of this review.