The road to hell is paved with online information Stuff sold as "tea tree oil" varies a lot in its concentration: if you had the real deal, full strength stuff, that would be a huge amount (and quite expensive for only 3 ounces of end product...probably cost you a lot more than Rocket Shower). I'd experiment with a modest (like 5 drops) of tea tree oil (whatever kind you're using) added to 3 ounces of witch hazel and see how that goes...increase as needed, but then, why do you need it? It's an antifungal/antibacterial, so unless your skin is septic, it doesn't seem like it's really necessary.