<s>[INST] Why do I need to arrange for periodic blood tests during prolonged therapy of Piriton? Why do I need to arrange for periodic blood tests during prolonged therapy of Piriton? [/INST] HI Thanks for the question. Portion contains chlorophrniramine, an antihistamines, h1 antagonist, which itself directly donor have any side effects on blood counts. But, your doctor might have suggested this for the reason that if you are suffering from any allergic conditions where blood counts are abnormal (e.g. high eosinophil count in allergy where portion is prescribed). In such cases you may need to do periodic blood tests to assess the improvement of the disease process. Hope I could answer your question. Wish you a speedy recovery. </s>