Latin name: Gallus domesticus
Source material: nGal d 1 is purified from egg extract
Egg allergen components
Hen’s egg comprises about 8-11% shell, 56-61% white and 27-32% yolk. The white is essentially an aqueous protein solution (10% protein and 88% water), and the yolk is composed of 50% water, 34% lipid and 16% protein, giving it quite different properties (1-2).
Egg white is the common name for the clear liquid (also called the albumen) contained within an Egg. It is the cytoplasm of the Egg, which until fertilisation is a single cell (including the yolk). Egg white is approximately 88% water and 10% protein. Its primary natural purpose is to protect the Egg yolk and provide additional nutrition for the growth of the embryo, as it is rich in proteins and is of high nutritional value. Unlike the Egg yolk, it contains a negligible amount of fat. Fifty-four percent of Egg white protein is composed of the major protein albumin (Ovalbumin). Other major proteins here are Conalbumin (Ovotransferrin) (12%), Ovomucoid (11%), Ovomucin (3.5%) and Lysozyme (3.4%). Other proteins have also been identified in Egg white: ovoinhibitor, avidin (0.5%), ovomacroblobulin, G2 and G3 globulins, and cystatin. Ovoflavoprotein is found in Egg white and yolk (3-4).
The Egg yolk serves as the food source for the developing embryo inside. Prior to fertilisation, the yolk together with the germinal disc is a single cell. The Egg yolk is suspended in the Egg white (known more formally as albumen or Ovalbumin) by 1 or 2 spiral bands of tissue called the chalazae. Yolk contains all of the Egg’s fat and cholesterol, and almost half of the protein. Egg yolk contains approximately 50% water, 16% protein and 32-35% lipid (4). Egg yolk can be separated into 2 fractions. The granule fraction contains 60% protein and 35% lipid, whereas the clear supernatant (the plasma fraction) contains 18% protein and 80% lipid. The granule fraction contains lipovitelin, phosvitin (16%) and lipoprotein (different from the lipoprotein found in Egg white). Phosvitin is the iron-carrying molecule of the yolk (4).
The total number of Egg proteins is not known, but more than 40 have been suggested for Egg white alone (5), and up to 24 different antigenic protein fractions have been isolated.
Characteristics of the Major Egg Proteins are presented in Table 1.
Egg white has been considered the most important source of allergens, but IgE-binding allergens have also been described in the yolk, suggesting that both common and distinct allergenic molecules are present. This was demonstrated in a study of 11 patients with a history of Egg allergy, in all of whom sera reacted positively to both white and yolk. Eight patients reacted equally or more strongly to white, and even though white and yolk could to some degree each inhibit the IgE binding of the other, yolk could be only partly inhibited by white in 8 sera (6).
Even though Ovalbumin is probably one of the most studied antigens in immunology, it does not appear to be the most allergenic molecule in humans. In a study of 34 adults with confirmed Egg allergy, Conalbumin (Ovotransferrin) and Ovomucoid were demonstrated to be the most prevalent allergens. Using the agreement between 2 or more of 4 laboratory methods as a criterion for evidence of sensitisation, the frequency of reactivity was found to be 53% (Conalbumin), 38% (Ovomucoid), 32% (Ovalbumin), and 15% (Lysozyme) (7).
However, different reports have emerged on the relative importance of the various allergens in Egg white. Some of the differences may be due to the studies of different populations. For example, it is likely that the Egg proteins are processed differently in the digestive system of infants and adults. A rigorous purification of the reagents may be necessary to obtain pure proteins, since commercial preparations of individual Egg white proteins may be somewhat contaminated (8).
The main allergens in Egg are found in the Egg white, but Egg yolk also contains a large portion of specific IgE-binding allergens (9). Gal d 1, Gal d 2, Gal d 3 and Gal d 4 are the most important allergens in Egg white. All are glycoproteins. Ovomucoid makes up approximately 10% of Egg white and is often regarded the major allergen (10-11).
Cross-reactivity has been shown among Conalbumin (Ovotransferrin), Ovomucoid and Lysozyme, and between Ovalbumin and the Yolk protein apovitellenin I. The cross-reactions among all of these proteins may signify that there is a number of common allergenic determinants on these Egg proteins, which gives a molecular basis for the phenomenon of cross-reactivity (4).
Allergens from Gallus domesticus listed by IUIS*
|Gal d 1
||Gal d 2
||Gal d 3
|Gal d 4
||Gal d 5
*International Union of Immunological Societies (www.allergen.org) Jan. 2008.
Table 1. Characteristics of the Major Egg Proteins.
|Egg white proteins||Heat sensitivity||Molecular weight (kDa)
|11% Ovomucoid (Gal d 1)
|54% Ovalbumin (Gal d 2)
|12% Conalbumin* (Gal d 3)
|3.5% Lysozyme (Gal d 4)
*also known as Ovotransferrin
Native protein purified from Egg white (Gallus domesticus)Biological function:
Ovomucoid, or Gal d 1, previously known as Gal d I or Gal d III, is a major allergen of Hen’s egg (1,8,10-11,14-15,23,25,33,45-53).
Ovomucoid is, together with Conalbumin (Ovotransferrin), the major allergenic protein in Hen’s egg. The highest concentration is found in Egg white. Ovomucoid is a unique Egg protein and is the dominant allergen in Hen’s egg, even though Ovomucoid comprises only 10% of total Egg white protein and Ovalbumin comprises >50% (25,52).
Ovomucoid is a highly glycosylated 28 kDa protein comprising 186 amino acids arranged in 3 tandem domains (Gal d 1.1, 1.2, and 1.3) (52). The amino acid sequences of the first 2 domains, Gal d 1.1 and 1.2, are 50% homologous, whereas <30% of Gal d 1.3 is homologous to Gal d 1.1 and 1.2 (54). The epitopes are conformational rather than linear, and the carbohydrate moieties have only a minor effect, if any, on allergenicity. Ovomucoid is highly homologous to pancreatic secretory trypsin inhibitor, although its trypsin inhibitory activity is confined to the second domain (55).
The significance of the 3 domains remains to be fully elucidated. In a study using serum samples from 45 patients with elevated serum-specific IgE to Hen’s egg (IgE >20 kUA/l), and with Egg allergy confirmed by DBPCFC conducted with direct ELISA to determine the percentage of patient Ovomucoid-specific IgE reactive with each of the 3 Ovomucoid domains, 42 patients had IgE antibodies specific to all 3 domains; 3 patients had no detectable IgE antibodies to Gal d 1.1. Although most patients had IgE antibodies to all 3 domains, the percentage of IgE antibodies directed to Gal d 1.2 was significantly greater (p < 0.05) than that to either Gal d 1.1 or 1.3 (52).
Ovomucoid is heat-stable (e.g., 100 °C for 1 h) and is not denatured by urea. It is resistant to protease digestion (56-57). The allergenic potential of Ovomucoid is thought to depend on its stability to heat treatment and digestion. When the digestion of Ovomucoid in simulated gastric fluid was kinetically analysed, 21% of the examined patients retained their IgE-binding capacity to the small 4.5 kDa fragment. Patients with a positive reaction to this small peptide fragment were thought to be unlikely to outgrow their Egg white allergy (45).
It has been suggested that Ovomucoid is the immunodominant protein fraction in Egg white and that the use of commercially purified Ovalbumin has led to an overestimation of the dominance of Ovalbumin as a major Egg allergen and antigen in humans (25).
As the stomach in newborn infants has little secretary pepsin and an out-of-optimum pH of peptic activity, Ovalbumin and Ovomucoid in raw and heat-coagulated Egg white are said to be poorly digestible at pH over 3.0, and this is purported to be responsible for their allergenicity and for the delayed outgrowth from Hen’s egg allergy in patients with delayed maturation of stomach functions. In a study of the peptic digestibility of raw and heat-coagulated Hen’s egg white proteins in the acidic pH range, Ovalbumin in raw Egg white was slightly digested by pepsin at pH 1.5 and pH 2.0, and was almost resistant to the enzyme at pH 2.5 and over. This was altered in heat-coagulated Egg white at the pH range from 1.5 to 2.5, where the protein was well digestive against the enzyme, whereas peptic digestibility of Ovomucoid in raw Egg white was good at the pH range from 1.5 to 2.5, but almost non-existent at pH 3.0 and over, where improvement of the digestibility of the protein was not found even in heat-coagulated Egg white (40).
Studies have elucidated the contribution of individual Hen’s egg components, e.g., Ovomucoid, to adverse clinical effects. Sensitisation and elicitisation of symptoms to Ovomucoid may occur through ingestion, inhalation or skin contact. The possibility of sensitisation due to Ovomucoid in house dust has been suggested (42), and Ovomucoid has been shown to be present in human breast milk (43).
In a study designed to determine the importance of Ovomucoid in the development of allergies to Egg white, a double-blind, placebo-controlled food challenge in subjects with high levels of IgE antibodies for Egg white was conducted to compare the allergenicities of heated and Ovomucoid-depleted Egg white, freeze-dried Egg white, and heated Egg white. Twenty-one of 38 subjects with positive challenge responses to freeze-dried Egg white had negative challenge responses to heated Egg white, whereas 16 of 17 subjects (94.1%) with positive responses to heated Egg white did not respond to the heated and Ovomucoid-depleted Egg white challenge. The subjects with positive challenge responses to freeze-dried Egg white tended to have higher IgE antibody values to Ovomucoid than did those with negative responses. IgE antibody levels to Ovomucoid were significantly higher in subjects with positive responses to a challenge with heated Egg white than in those with no response. The authors concluded that Ovomucoid has a more important role in the pathogenesis of allergic reactions to Egg white than other proteins in Egg white (33).
Subjects are often encountered without overt symptoms despite high IgE antibodies to Egg white and its components. The measurements of these antibodies are not necessarily efficient for the diagnosis or the prediction of the outcome of Egg allergy in children. A study measured specific IgE antibodies to Egg white and its components, including Ovomucoid, Ovalbumin, (Ovotransferrin), Conalbumin and Lysozyme, by direct RAST assays and by inhibition studies in 30 subjects who were divided into 2 groups with positive (n=18) and negative (n=12) oral challenge tests with Egg white antigens. The individuals with positive results to the first challenge tests were given the second provocation tests at mean intervals of 32 months. IgE-binding activity of the sera collected on the first challenge to these Ovomucoid fragments was compared between subjects with positive and negative reactions to the follow-up challenge tests. There were no significant differences in IgE antibody titers to Egg white and its components between the positive and negative groups at the first and the second challenge tests. IgE-binding activity to Ovomucoid digests after treatments with pepsin and trypsin, except chymotrypsin, were significantly higher in subjects with positive challenge tests than in those with negative results. The study concluded that IgE-binding activity to pepsin-digested Ovomucoid was of diagnostic value for distinguishing the challenge-positive subjects from the negative subjects, and that subjects with high IgE-binding activity to pepsin-treated Ovomucoid are unlikely to outgrow Egg white allergy (49).
Approximately two-thirds of Egg-allergic infants become tolerant within the first 5 years of life. A study sought to compare the recognition of sequential (linear) and conformational binding sites of Ovomucoid, Ovalbumin and Ovotransferrin (Conalbumin) by IgE antibodies of children with persistent and transient Egg allergy, to identify immunodominant IgE- and IgG-binding epitopes of Ovomucoid, and to compare epitope specificity of IgE antibodies between patients with differing histories of Egg allergy. Patients with long-lasting Egg allergy had higher concentrations of IgE antibodies against sequential and native Ovomucoid and Ovalbumin than did the children who subsequently gained tolerance (p < 0.01). Four major IgE-binding epitopes were identified in Ovomucoid. IgE antibodies of all 7 patients with persistent Egg allergy recognised these epitopes, whereas the antibodies in none of the 11 children who outgrew their Egg allergy did so. The study concluded that patients with persistent Egg allergy develop IgE antibodies against more-sequential and conformational epitopes of Ovomucoid and Ovalbumin, and that the presence of serum IgE antibodies to specific sequential epitopes of Ovomucoid may be used as a screening instrument for persistent Egg allergy (58).
Native protein purified from Egg white (Gallus domesticus)
Common name: Albumin
Biological function: Ovalbumin
Mw: 44 kDa
Gal d 2, also known as Ovalbumin and Albumin, is a 44 kDa phosphoglycoprotein (8,11-30).
Gal d 2 was previously known as Gal d I and Gal d II. An isoform, Gal d 2.0101, has been characterised.
Ovalbumin is a major allergen of Hen’s egg white and is the most abundant of Egg white proteins, comprising 54% of the total proteins and a fivefold greater quantity than Ovomucoid. It has 4 cysteine residues and a single cystine disulphide bridge. When Egg white proteins are separated by electrophoresis, 3 Ovalbumin bands appear, corresponding to the dephosphorylated, mono- and di-phosphorylated forms (12).
Ovalbumin was previously considered to be the most important allergen of Egg white. But its importance was over-estimated due to frequent contamination of commercial preparations with Ovomucoid (25). In spite of a difference in the molecular weights of Ovomucoid and Ovalbumin, they cannot be completely separated by some processes, which has lead to the erroneous assumption of cross-reactions.
Ovalbumin has homology with a group of proteinase inhibitors known as serpins. However, Ovalbumin does not have proteinase inhibitory activities (12).
Ovalbumin is also susceptible to proteolysis when treated with subtilisin. However, the cleaved product does not show a conformational change or a difference in heat stability (12). However, it easily aggregates and becomes difficult to extract by heating (31). Ovalbumin digestion in both simulated gastric fluid and simulated intestinal fluid has been demonstrated to be markedly decreased (32).
Although Ovalbumin is heat-stable, in a study the heated and Ovomucoid-depleted Egg white preparation was less allergenic than heated or freeze-dried preparations. Ovomucoid must have a more important role in the pathogenesis of allergic reactions to Egg white than do other proteins in Egg white (33). A more recent study indicated that heated and Ovomucoid-depleted Egg white was less allergenic than heated Egg white (34). It has been reported that Ovalbumin allergenicity could be effectively reduced by the combination of heat and gamma irradiation treatment (22). A study of Egg white proteins in an animal model suggested that over-cooking of proteins may affect their intestinal antigen processing and thus prevent the induction of oral tolerance (35).
Ovalbumin has the ability to cross the placenta in a dose-dependent and molecular-weight-dependent manner in full-term and premature babies, with clear accentuation in preterm placentas, and may provide the foetus with the necessary stimulus for T cell priming or potential sensitisation (36-38).
Ovalbumin has also been shown to cross into human breast milk and may result in sensitisation that elicits symptoms in the infant. In a study to determine whether the concentration of Ovalbumin in human milk is directly related to the quantity and form of Egg consumed by breastfeeding mothers, 41 breastfeeding women were randomly allocated to receive a test breakfast, identical except for the Egg content (no Egg, 1 raw Egg, half a cooked Egg or 1 cooked Egg). There was a response directly dose-dependent on the amount of cooked Egg ingested and the peak Ovalbumin concentration (no Egg, 0.05 ng/ml; half a cooked Egg, 2.24 ng/ml; 1 cooked Egg, 3.16 ng/ml), as well as on the total Ovalbumin excretion (no Egg, 0.18 ng/ml/h; half a cooked Egg, 4.93 ng/ml/h;
1 cooked Egg, 9.14 ng/ml/h). There was no detectable OVA in the breast milk of 24% of the women (10/41) up to 8 hour after any Egg challenge (39).
As the stomach in newborn infants contains little secretary pepsin and has an out-of-optimum pH of peptic activity, there is low digestibility of Ovalbumin and Ovomucoid in raw and heat-coagulated Egg white at over pH 3.0, and this is supposed to be responsible for their allergenicity and for the delayed outgrowth from Hen’s egg allergy in patients with delayed maturation of stomach functions. In a study of the peptic digestibility of raw and heat-coagulated Hen’s egg white proteins at the acidic pH range, Ovalbumin in raw Egg white was slightly digested by pepsin at pH 1.5 and pH 2.0, and was almost resistant to the enzyme at pH 2.5 and over. This was altered in heat-coagulated Egg white at the pH range from 1.5 to 2.5, where the protein was well digestive against the enzyme, whereas peptic digestibility of Ovomucoid in raw Egg white was good at the pH range from 1.5 to 2.5, but almost non-existent at pH 3.0 and over, where the improvement of the digestibility of the protein was not found even in heat-coagulated Egg white (40).
Studies have elucidated the contribution of individual Hen’s egg components, e.g., Ovalbumin, to adverse clinical effects. Sensitisation and elicitisation of symptoms to Ovalbumin may occur through ingestion, inhalation or skin contact. Adverse effects have been documented to the ingestion of as little as 10 mg of Ovalbumin (41). As sensitisation due to Ovomucoid in house dust has been suggested (42), and as Ovomucoid has been shown to be present in human breast milk (43), both may also be true for Ovalbumin, although neither has been evaluated yet.
Egg-allergic children may occasionally develop contact urticaria to Hen’s egg and yet have no overt symptoms on ingestion. In a study to investigate possible mechanisms, 21 subjects with positive reactions to patch tests with Egg white allergens were divided into subgroups with positive (n = 10) and negative (n = 11) results to oral challenge tests with the same allergens. There were no significant differences in serum-specific IgE levels to Egg white (positive vs. negative: 30.3% vs. 15.3%), Ovomucoid (21.5% vs. 10.2%), Ovotransferrin (Conalbumin) (9.9% vs. 3.7%), and Lysozyme (3.4% vs. 2.9%). But in the case of Ovalbumin (16.8% vs. 5.6%), there was a difference between the positive and negative subjects in the provocation tests. The study suggested that IgE antibodies from subjects with contact urticaria to Hen’s egg but tolerance to ingestion of Egg white recognise the epitope(s) unstable to digestive enzymes (44).
In a study suggesting that Egg contributes to the development of atopic dermatitis in younger infants by inducing the production of IL-5 but not IL-4, the results demonstrated that Ovalbumin-induced IL-5 production fluctuates with age in a different manner than IL-4 or Egg white IgE (24).
Native protein purified from Egg white (Gallus domesticus)
Common name: Ovotransferrin, Ag22
Biological function: Conalbumin
Mw: 66-78 kDa
Gal d 3, also known as Conalbumin, Ovotransferrin, and previously as Ag22, is a 66-78 kDa protein (8,11-12,14-16,35,59-64).
Conalbumin is a glycoprotein which is present in Egg white, Egg yolk, and plasma. The proteins from all 3 sources have the same amino acid sequence, but there are slight differences in the glycosylation. The protein is made up of 2 domains with a short linking region. Each domain has a very strong binding site for iron. There is about 40% homology in the sequences of the 2 domains. The function of Conalbumin is generally accepted as being iron transport. It binds 2 atoms of iron, 1 in each domain (12). Conalbumin has complex disulfide and bilobal structures, which are derived from the same gene as Chicken serum transferring (59).
In a RAST inhibition study with heat-treated Egg white allergens (100 °C, 5, 10, and 30 minutes) performed on 13 serum samples from subjects with immediate hypersensitive reactions and 9 serum samples from subjects without immediate hypersensitive reactions, it was demonstrated that heat treatment decreased the IgE-binding activity of Egg white. When the individual allergens were assessed, IgE-binding activities to Egg-White components, including Ovalbumin, Conalbumin, and Lysozyme but not Ovomucoid, were significantly decreased with heat treatment (30). Although heat denaturation of proteins can minimise allergenicity, a study suggested that over-cooking of proteins may affect their intestinal antigen processing and thus prevent the induction of oral tolerance (35).
Only partial cross-reactivity has been demonstrated between Chicken serum albumin and Conalbumin (65).
Transferrins are an important class of iron-binding proteins widely distributed in the physiological fluids of vertebrates and invertebrates. In vertebrates they are present mostly in serum, as serotransferrins. In birds and reptiles transferrins are also found in Eggs as Conalbumins. A study demonstrated significant homology of Conalbumin among red-eared turtle, African ostrich and Turkey, but allergenic potential was not investigated (66).
Native protein purified from Egg white (Gallus domesticus)
Biological function: Lysozyme
Mw: 14 kDa
Lysozyme is an enzyme that consists of 129 amino acids cross-linked by 4 disulfide bridges. Lysozymes are small globular proteins found in animal tissues, organs and serum as well as in tears, milk, saliva, nasal secretions and cervical mucus. Lysozymes differ from species to species. Lysozyme also occurs naturally in many organisms such as viruses, plants, insects, birds, reptiles and mammals.
Egg lysozyme is also known as Gal d 4 (see below) and is a potent allergen (28).
The major source of commercial Lysozyme, in particular for pharmaceutical use (where it is known as Lysozyme chloride or Lysozyme hydrochloride), is extraction and purification of Hen egg albumen. Lysozyme concentration in Egg albumen is about 0.5% (67). Lysozyme chloride is usually extracted from fresh Egg white by means of a biotechnological process. One method involves a food-grade inert material (a polymer resin) being mixed with the Egg white, where it binds specifically with the Lysozyme. The resin carrying the Lysozyme is then stripped off, concentrated, purified and dried. The dried, purified protein is almost 100% Lysozyme chloride. The substance is heat-stable (80 °C for 2 minutes). It is inactivated at lower temperatures with increased pH. The optimum temperature for activity is 55 to 60 °C (67).
Gal d 4, Lysozyme, is a 14.3 kDa protein (8,11,14-16,68-70).
Lysozymes are small globular proteins and may be found in many other animal tissues, and in tears and saliva. They differ from species to species (28). Lysozyme has also been described as a defence-related protein found in Latex and a number of fruits. Latex and Fruit lysozyme is enzymatically very similar and has been demonstrated to be allergenic. However, this Lysozyme is not the same as Egg lysozyme (71).
Lysozyme is an allergen for some patients (9). Additionally, Lysozyme per se may be used as an additive and through this route may uncommonly induce symptoms of food allergy in sensitised individuals. However, Lysozyme has been reported to be a more common allergen in occupational settings, resulting in adverse effects following skin contact or inhalation.
Early studies reported that, due to its protein nature, Lysozyme has immunogenic properties and can provoke anaphylactic reactions (72-73). But its potency was regarded as moderate and considerably lower than that of other proteins such as Albumen and Ovalbumin. Hen’s egg lysozyme was initially thought to be a minor problem: patients who experienced adverse reactions after consumption of Eggs most frequently showed IgE antibodies to one of the many protein components of Egg white, but very rarely to Egg white lysozyme (28).
However, a more recent study found that, with 31% of food-allergic children and 8% of food-allergic adults being allergic to Egg, out of 52 patients clinically allergic to Egg, 35% had anti-Lysozyme IgE. The authors concluded that, because of this high incidence of Lysozyme sensitisation, the presence of Lysozyme as an additive should be indicated on food labels (74).
Allergy to Lysozyme may be more frequent than has been previously documented. Over a period of more than 10 years (1990-2002), 171 cases of adverse reaction to food were registered by the Swedish authorities; 5 of 21 cases of allergic reaction to Egg were attributed to Lysozyme as an additive to cheese (75).
Lysozyme has often been used as a preservative in the pharmaceutical industry, and drug allergy to Lysozyme preparations has been reported (76). Hen’s egg white Lysozyme has also been commonly used in some countries to treat diseases of the respiratory tract. In a study examining Egg-specific IgE in patients with Egg allergy, and in patients with allergies other than to Egg, high levels of allergen-specific IgE to Lysozyme were found in 30 out of the 39 patients allergic to Egg. The study also described a patient with anaphylaxis following exposure to Lysozyme, who had a level of 1.0 (PRU/ml) of IgE antibodies to Lysozyme. The authors cautioned against treating allergic patients with Hen’s egg white lysozyme (77).
A pharmaceutical industry worker developed occupational asthma and rhinitis from both serratial peptidase and Lysozyme chloride. Skin prick tests were strongly positive to peptidase and Lysozyme extracts, and bronchoprovocation tests showed an immediate and delayed asthmatic response to peptidase, and an immediate asthmatic response to Lysozyme. Allergen-specific IgE antibodies to peptidase and Lysozyme were detected (78).
Initially, Lysozyme was considered of little significance as an allergen because of its thermolability (14), but the presence of IgE antibodies to Lysozyme was found to be common in Egg-processing workers (79-80). Occupational asthma resulting from the inhalation of Egg lysozyme was described in a 26-year-old man employed in the manufacture of Hen’s egg white-derived Lysozyme for use in the pharmaceutical industry. He began to experience immediate-onset asthmatic symptoms 2 months after starting to work with Egg lysozyme powder. Skin prick test was positive to Egg lysozyme and other Egg proteins, but negative to whole Egg white and Egg yolk. Serum-specific IgE to Egg lysozyme was found. A specific bronchoprovocation challenge to Lysozyme powder was positive, resulting in an immediate asthmatic response (81).
Inhaled allergens are a serious problem in the bakery and confectionery industries. Sensitisation to Wheat flour and enzymes such as a-amylase is a frequent cause of occupational asthma (82). Bakers are often exposed to aerosolised Egg allergens. In a study of 4 bakery workers who had developed work-related allergic respiratory symptoms upon exposure to Egg aerosols, skin-reactivity to Egg white extract and to Lysozyme was detected in all the workers, to Ovalbumin in 2, to Ovomucoid in 1, and to Egg yolk in 2. They were additionally sensitised to Wheat, Rye and Barley flour.
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