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| Allergen Data Collection - Update:
Cow's Milk (Bos domesticus) ...................................................... |
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Abstract
Cow's milk allergy (CMA) can be defined as
any adverse reaction mediated by immunological mechanisms to cow's milk
proteins. CMA can be divided in IgE-mediated reactions (IgE-CMA) and non-IgE-mediated
reactions (non-IgE-CMA) which may involve other immunoglobulins, immune
complexes and cell-mediated reactions. Patients with non-IgE-CMA and digestive
symptoms can present with the following well defined clinical pictures:
milk- induced enterocolitis, milk- induced proctitis, milk- induced enteropathy,
or eosinophilic allergic gastro-enteritis. CMA should be differentiated
from cow's milk intolerance (CMI) reactions due to lactase deficiency or
other non immune mediated causes which are not subject of the present review.
Most CMA has its onset in the first year of life, and becomes apparent
at the time of weaning from breastfeeding.
Prevalences of CMA range from 1.6% to 2.8%
in randomly selected children younger than 2 years of age (elimination
/ challenge proven). Oral tolerance is frequently acquired in about 50
to 90% of children with CMA within the first 6 years of life. However,
severe CMA may persist into adulthood. The frequency of sensitization to
cow's milk in adults has recently been estimated by RAST to be 0.7% and
1.2% in Scandinavian countries.
According to the onset of symptoms after milk
ingestion CMA can be classified as immediate or delayed- type. The clinical
picture can vary from mild to severe, involving the skin (eczema, hives,
angioedema), gastrointestinal tract (oral pruritis, colic, vomiting, diarrhea,
constipation), respiratory tract (cough, stridor, wheezing), and
cardiovascular system (anaphylactic shock).
No single laboratory test is diagnostic of
CMA. Clinical manifestations supported by skin tests and in vitro parameters
are valuable. The diagnosis is confirmed by well-defined elimination and
subsequent challenge procedures. If there is evidence of anaphylaxis, challenge
should be avoided. The inadvertent ingestion of small amounts of cow's
milk allergens hidden in foods can result in severe life- threatening clinical
reactions. Cow's milk allergens could be present in breast milk, infant
formulas, milk and milk products like cheese and yogurt, as well as in
"non-dairy" foods occurring as contaminants or unlabeled additives. The
most effective treatment of CMA is allergen avoidance. Besides the optimal
choice of breast milk, suitable milk substitutes in the nutrition of infants
with CMA are soy hydrolyzed formulas, extensively casein and whey hydrolyzed
formulas, and amino acid formulas. The exact frequency of sensitization
to soy protein in children with CMA is still controversial. Soy allergy
seems to be rare in IgE-CMA, while approximately 60% of children with milk-
induced enterocolitis are sensitive to soybean. However, severe anaphylactic
reactions to extensively hydrolyzed casein and partially hydrolyzed whey
formulas can occur in highly sensitized infants with IgE-mediated cow’s
milk allergy. Due to the high homology of protein composition sheep's and
goat's milk are cross-reactive in approximately 80% of subjects with CMA
while mare's milk is only rarely cross-reactive with cow's milk (4% in
subjects with CMA). In addition, sheep’s milk may cause severe IgE-mediated
allergic reactions in children not affected by CMA. IgE antibodies from
children allergic to cow’s milk are capable of recognizing milk proteins
from mammals bred in European countries (ewe, goat, buffalo). Cross-reactivity
of camel’s milk proteins has not been recognized. Therefore, due to clinically
important residual allergenicity in some hypoallergenic formulas and milk
allergen cross-reactivity between species, clinical testing in a safe medically-supervised
environment is necessary in each cow’s milk sensitive infant before use.
In infants and children the major cow's milk
allergens are casein (CAS), beta- lactoglobulin (beta-LG), and alpha- lactalbumin
(alpha-LA). Caseins (alpha-, beta-, kappa-CAS) are the most important in
children and adults. Other allergens involved in CMA are bovine serum albumin
(BSA) and bovine immunoglobulins. Several IgE- binding epitopes of alpha-LA,
beta-LG, alpha- and beta-CAS have been described. Knowledge of the immunodominant
epitopes of the major allergens may be useful in identifying children who
will have persistent CMA and children who are likely to outgrow CMA.
The present data collection summarizes the
following topics in tabular form: prevalences of CMA, diagnostic and therapeutic
features, molecular biological and allergenic properties of cow's milk
allergens, stability and hidden presence of allergens, the use of infant
formulas in therapy and prevention of CMA and other atopic diseases.
Disclaimer
The reference lists of the Allergen Data Collections
are based mainly on searches of Medline and FSTA (Food Science & Technology
Abstracts) databases up to the related dates of publication. The scientific
rigor of the studies listed is variable and not subject of critique or
evaluation by the authors or the editor of the Allergen Data Collections.
The reader should be aware of considerable problems in comparing data from
different studies (eg. patient cohorts, diagnostic performances, possible
flaws in allergen preparations and methodologies for allergen characterization)
and is encouraged to review the original publications.
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