I do not know much about the inhalation technique, except according to (old) medical literature, it has helped many people with obstructive pulmonary diseases.
I do know it MUST be food grade HP, and the mixing water (if needed) MUST be distilled (chlorinated water creates a poisonous gas).
The other problem might be the concentration. In general human cells use the enzyme 'Catalyse' to convert excess HP into oxygen and water (the bubbling seen when applied to wounds- this does NOT kill the bacteria, another mechanism does). Unless you are chronically low in catalyse (extremely rare), your cells should not be damaged at low concentrations. However you should not take any 'metal' based supplements at all, especially iron, whilst doing HP. That is the advice when drinking it in any case, could well not matter for pure inhalation. Personally I would (and do) also drink it - but make sure it is done in the right way. I will only drink once a day when waking- any other time and the stomach will not be empty. Maybe, if you tried the drinking protocol, it would help without ever having to inhale it.I cannot see how it can be an allergic reaction since HP is used in just about every cell/fluid in the body. It is also found in fresh fruit/veg, honey - just about everything. But in minute amounts. That said, the symptoms sound severe - and as another poster implied even possibly dangerous. Perhaps you could find a doctor that performs HP therapy.One of the first indications that it is working should be coughing up a load of, well, toxins.