I am sensitive to milk, including whey protein. It affects my skin and also causes sinus congestion. I haven’t tried to put back in casien like Metabolic Drive, but partially hydrolyzed whey seems to cause the same effects.
On the other hand, Mag-10 does not seem to cause any problems. Based on the label, it is supposedly completely hydrolyzed down to 2-3 amino acid length peptides which would mean that large milk proteins that can cause sensitivities are all broken down.
Studies with infants with proven cow’s milk allergy have shown that extensively hydrolyzed whey does not cause allergic responses in about 95% of subjects. https://www.ncbi.nlm.nih.gov/pubmed/11338291 Biotest BCAA structured peptides would fit the definition of extensively (or completely) hydrolyzed whey based on the label. Mag-10 would be defined as extensively (or completely) hydrolyzed casien based on the label. I have used both of these products and they do not cause the same sensitivity issues as milk. I have tried whey proteins that would be assumed to be partially hydrolyzed and was sensitive to them.
Oddly, cheese does not seem to cause any issues, or if so they are mild effects so I considered that it might be the lactose, but even whey with no lactose does cause it. Hard cheeses have the whey removed and are mostly casien so again, maybe I’m sensitive to large proteins in the whey. For that reason, you may want to try casien based protein like Metabolic Drive, especially if you are OK with hard cheese. Mag-10 is hydrolyzed casien and also highly hydrolyzed and BCAA structured peptides are hydrolyzed whey.
My advice is to try a pure casien source, unless you know that you are sensitive to hard cheese, in which case, casien may be a culprit, OR to try an extensively hydrolyzed product, which has additional advantages that it has an extremely high absorption rate due to being broken down to small peptides. Third might be to try an egg protein source or to simply do with whole foods. I think that hydrolyzed milk proteins are beneficial if tolerated (both hydrolyzed whey and casien have been proven to have benefits) but if you are turning to plant based proteins, then I would just go with more protein from food instead.