Allergy to cow’s milk is the most common form of childhood allergy. Incidence of this particular allergy is approximately 2 – 3% in developed countries. Symptoms in infants range from 5 to 15%. Children generally develop symptoms within a week of being introduced to cows’ milk. Symptoms of cow’s milk allergy may take different forms including:
- cutaneous in about 50 – 70%
- gastrointestinal in 50 – 60%
- respiratory in 20 – 30%
There are two types of milk allergy, transient and persistent. While some children have a life-long allergy to milk, many children outgrow their childhood milk allergy in that
- 45 – 50% outgrow this allergy by 1 year
- 60 – 75% outgrow this allergy by 2 years
- 85 – 90% outgrow this allergy by 3 years of age.
It has long been known that heat changes the protein so researchers challenged children with a milk allergy with milk that had been extensively treated with heat. Nowak-Wegrzyn and colleagues reported on their research in the Journal of Allergy and Clinical Immunology.
The researchers looked at 100 children with a milk allergy between the ages of 6 months and 21 years. Skin prick tests were used to confirm the allergy. They challenged them initially with heated milk products in the form of a muffin. This was given in 4 small doses. If there was no reaction they were challenged 2 hours later with a waffle. Children who tolerated both the muffin and the waffle were considered heat-tolerant and were challenged with heated milk.
Of the children, 68% tolerated heated milk, 23% reacted to heated milk and 9% tolerated both heated and unheated milk. The study continued with the heated milk-tolerant children ingesting heated milk products for 3 months before final evaluation. The researchers concluded that 75% of the children tolerated heated milk. Children who reacted to heated milk had more severe symptoms during heated milk challenge than children tolerant to heated milk had when challenged with unheated milk.
So, in some cases, the allergenicity of milk proteins can be modified by extensively heating the milk. It is important to note that heating decreases but does not completely eliminate milk allergens. The researchers warned that there was no certainty that tolerance to heated milk would result in permanent tolerance to unheated milk.
Host A, Halken S1. Cow's Milk Allergy: Where have We Come from and Where are We Going? Endocr Metab Immune Disord Drug Targets. 2014 Jan 21. Abstract.
Nowak-Wegrzyn A, Bloom KA, Sicherer SH, Shreffler WG, Noone S, Wanich N, Sampson HA. Tolerance to extensively heated milk in children with cow's milk allergy. J Allergy Clin Immunol. 2008;122(2):342-7