I took an Allegra at 8 A.M. If I took an Excedrin now, would it knock me out, make me loopy, cause a subdural hematoma, anything? Excedrin contains, according to the label, aspirin and caffeine in addition to the acetametophin.
Bad headache- requesting assistance!
Unless you have impaired renal function, you should be fine to take this together. This link from the Discovery Channel drug interaction checker says it’s fine. Just stay away from grapefruit juice.
Just to note: not a doctor nor a pharmacist. But I know my antihistamines. 
I’m a doctor, but this is not medical advice: you’re not my patient; I haven’t examined you; and I don’t know your medical history.
It sounds fine to me.
I just popped in to note that “Pharmacologically Minded Dopers” usually means someone who cooks up his own drugs.