Passiveness and lethargy are side effects of drugs like Avil and this side effect can be more pronounced in some individuals. I would suggest:
1) Use of other antihistamines like fexofenadine,laevocetrizine etc.
2) Some individuals may show a good response to medicines like monteleukast.
Feeling of acidity can occur with some B complex preparations and again there can be inter-individual variability. There is no correlation between symptoms with anti-histaminic agents like Avil and B complex.