Lately, it seems that I've developed an allergy to shellfish because I started getting mild reactions to my glucosamine supplement (mild, meaning light itchyness on the outside of my neck with a light rash in the same area which goes away after a couple of minutes).

I want to continue taking it because it's worked great for me.

But, if my body is reacting to it, does it mean that it cannot digest it, or process the nutrients from it?