I noticed allergies has 180 mg where as claritin (loratadine) and zyrtec says 10mg .does this mean allergra is stronger ?

Yes and no: The mg per se means nothing , it is the biologic or chemical activity that matters. For example, a ton of TNT will be far less powerful than a pound of uranium when used as an explosive. On the other hand, I personally believe that Allegra overall has a little more anti-histamine activity than Claritin (loratadine) but not necessarily Zyrtec.