I wash mine every other day and use henna shampoo and cond. from whole foods.  I do not think I have an issue with it , but my bladder has been bad the last few weeks so, I really cant tell what it is, but I am thinking it is just die off and not the shampoo since I have used it before having these bad bladder days.

i was my hair every 2 days with black soap I use the bar i know it sounds weird but it's the only thing that works and doesn't bother my urethra at all also this soap has no chems they use plants even to ph it no LYE at all. Best of all i pay about 4. for it and it is 4 oz bar.  I use this on my body too i did buy there liqud one it didn't work as well.
http://www.africaimports.com/Itemdesc.asp?ic=M-S498&eq=&Tp=
THe condioner i get is also from African imports and is a base unsented conditoner meaning not a brand name it is used to make condtioner all i add is 5 drops of lavender to mine. It lasts me 3 months i have short hair. The black soap lasts me one month I buy 3 of them at a time.
http://www.africaimports.com/itemdesc.asp?ic=M-431&eq=&Tp=
Nicole

that neem shampoo bothers my urethra I can't use it. I wash my hair every 2 days sometimes every other day depending on life.

I have long hair and coat it with conditionner before washing my scalp with shampoo. This protects the lenght of my hair from getting over dried.I like Avalon Organics unscented shampoo and conditionner, among others. You could also put olive oil in your lenghts the night before you wash your hair.Or Jojoba Oil. If you do this a few times in a row, (leave out the scalp, in your case) your hair will look better quickly.Also, I always leave a little conditionner in my lenghts (not the roots), to keep them moisturized. Hope this helps you a little.Hugs, B