Help with answers for a strange occurance

I've had an ileostomy for 30 years.  Over the past several months my one piece applaice began to develop blister.  The appliance itself started devopling blisters on it similr to what you might see on bubble wrap.  Thinking the appliance may have been faulty I started using a different brand of appliance.  The same thing occured only sooner with the new brand.  Does anyone have any direction?