Can someone tell me if senna teais safe to drink every other day?

I wouldn't recommend: "irritant" purgatives cause: melanosis coli (reversible pigmenting of colon lining) which is often seen with chronic senna use, cathartic colon ("floppy" colon with limited muscle tone), & soap or chemical colitis (acute inflammation within hours of "cleansing" enema). See my earlier healthtap answers regarding the longterm systemic consequences of chronic laxative use / overuse.