humidity level? stuffy nose
There is no one appropriate humidity level. In the dry, cold north household humidity must be below 20% during certain weather to prevent massive condensation on windows, which can result in damage. Here's a chart showing approximate levels for different outside temperatures:



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I agree with the comments above indicating that you likely have an allergen issue. Moisture alone doesn't typically result in respiratory distress. Lack of moisture can certainly be irritating, however.