Have never heard/read that and that wasn't my experience back when I used to use regular color instead of henna . . . Not saying you didn't read something like that here - I probably never see 95% of the posts, LOL!
2C/3A/3B - modified CG - med./fine, normal/low porosity/normal elasticity

Current Main Rotation: MG217 medicated or Aim2Health 'poos for scalp, YTCarrots or Elucence cond., Spiral Solutions Protein & Deeply Decadent Cond., CJCCCC reg or lite, KCCC, Giovanni LA Hold Hair Spritz + lots more, sporadically

HG Method: Super Soaker + Smasters-ing, brief upside down diffusing w/360o diffuser then clips/clamps & air dry. Newly gray - stopped my henna glosses!

www.fotki.com/auntnett