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 what causes IgE allergic reaction to cow’s milk, with most people being allergic to casein proteins in the milk.
I have put together some more comprehensive resources at http://www.allergyresources.co.uk/Cow-Milk.php
The allergy resources page for cow’s milk covers the key allergens, which allergic syndromes are linked to this allergy and other foods which are commonly cross reactive with cow’s milk .
There is also regularly updated links to useful websites specifically for cow’s milk allergies and the latest research papers on the topic.
If you have multiple allergies and are interested in how they are linked or want to find out more about food allergies outside the usual top 14 then you can follow me on Facebook or Twitter, where I share a food allergy card every day of the week.