Can allergies make you swell up and retain water? I notice when I take Claritin it lasts longer than Benadryl (diphenhydramine) and im not retaining fluids as much

Unexpected. If you mean swelling which lasts hours at a time, it is not from water retention and is called angioedema. Water retention tends to be most noticeable at the legs and ankles and would dent if you press your finger against the area. Claritin does not relieve water retention but may reduce angioedema and yes it has a longer duration of action than benadryl (diphenhydramine).