Well, any chemical drain opener is potentially dangerous. I just don't really like the acid ones at all. And I'd like muriatic (HCl-based) ones even less. Usually you don't even find them in stores here because most people with no chemical training honestly shouldn't be using such hazardous chemicals. Personally I'd stick to the alkaline ones or even better, use mechanical openers.
As for your condition, the forum has a policy of not offering medical advice of any kind. I could tell you I think you'll be OK, but if I did and then you turned out not to be, that'd be a source of liability - and I'd also feel pretty bad about it.
So! You should really be getting that kind of information from your doctor, who is better equipped to evaluate your health. If you aren't satisfied with the doctors you've already seen, you can always seek a second opinion.