I dont know to be honest. I think the vehicle is really important with cetirizine and of course you need to try it for six months. I imagine that if you wanted to take it orally you might need to take a much higher dosage than the recommended. Like Seti.
Topically i use it 2% and it helps. I dissolve 240mg of cet powder in 6ml distilled water. I then slowly add 2ml PG and about 4ml of neogenic capsule. This is the current vehicle i am using and it works well. Not greasy at all. Batches only last 4 to 5 days which is good as apparently cetirizine can degraded in ethanol.
What does ceti do for you? How long have you been using it?