Venom Immunotherapy

I'm more than a bit confused and frustrated - hoping for some guidance. My husband has been undergoing venom immunotherapy for approx. 10 years after systemic reactions to wasp/hornet stings. Receives treatment for wasp and mixed vespids. Over the 10 years, his response to treatment has actually been getting worse not better! After his start of treatment he was tested after 3 years and told he was still highly allergic and needed to continue treatment; three years later - he had actually gotten worse (in terms of the skin/blood test results) which was something the office manager said she had never seen in 20+ years; now, another 3 years later he is re-tested and told he is even worse than before and is now showing high sensitivity to honey bees as well (they now want to add that to his regime). I don't see how this is happening while he is undergoing treatment or, conversely, if it is not helping and is in fact hurting why should he continue? At this rate, he'll be a -3 vs. a 1! I'd appreciate any help understanding what to do. Thanks.