There are 12 allergens associated with cows, 9 of them relate to an allergy to the milk they produce (rather than the consumption of meat they produce).

The allergenic proteins in cow's milk are generally split into albumins (commonly called whey) and casein. In human milk the split is usually 60% whey to 40% casein. In cow's milk the split is 20% whey to 80% casein. This massive difference in composition is thought to be the cause of IgE allergic reaction to cow's milk, with most people being allergic to casein proteins in the milk.

Cow's Milk Protein Allergy (also called CMPA) is not be confused with lactose intolerance. A true allergy is to proteins in a food, lactose intolerance is due to a reaction to sugars in milk. Lactose free products should not be used by people with an allergy as they may still contain proteins - always check your labels!

Cross reactivity is usually caused by the proteins in one food being similarly shaped to those in another food. Unusually there is cross reactivity between the seed storage proteins in soya beans and the casein in cows milk. This is called non-homologous cross reactivity. This is a common anecdote, that babies allergic to cows milk can often not tolerate soya milk either and this would be the reason.

Cow's milk is usually the first food for many babies, which is why it seems such a common allergy. It is advisable to see your GP or health provider if your baby has an allergy as many very young children with a milk allergy will outgrow it.

Fresh pasteurised cows' milk is low in histamine, so is suitable for people following a low histamine diet, however the histamine levels increase once it is made into yoghurt and even higher once made into various cheeses.

Milk is a high FODMAP food. FODMAP stands for Fermentable oligosaccharides, disaccharides, monosaccharides and polyols. Foods high in FODMAPs can cause symptoms of food intolerance, affecting the gastro intestinal system and this can be mistaken for a true IgE food allergy.

Cow's milk allergy is not currently associated with any allergic syndromes.

There is a lot of evidence of cross reactivity between cow's milk and eggs and this is due to serum albumin proteins found in both.

About 13 - 20% of cow's milk allergy sufferers will also react to beef when consumed. This is, again, due to serum albumin proteins found in both foods.

Cow's milk allergy has also been linked to a soya allergy - the soya protein component that cross-reacts with casein has been identified as a glycinin molecule.

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