Suggest Treatment For Itching On Body After Taking Zyrtec And Ranitidine

I have had an allergic reaction to something, perhaps food additives per my doctor...He prescribed Zyrtec (take in am) and Ranitidine(take before bed)...I thought I read that you can take Zyrtec every 6-8 hours....so I took another one this afternoon(6hours later) because my itchy symptoms were getting worse....now as I m looking at the label it says not to take more than 1 per day....now what? A little nervous!