If you have psoriasis in your scalp, this shampoo might be your savior. it has been and is for me. I lather up my hair and leave it on for 10-15 minutes while I shave in the shower. 2-3 minutes just doesn't get the same excellent results as a bit longer contact. A tube lasts for many shampoos, perhaps 15-25 depending on your hair's length and volume.