Henna is a plant compound that’s used to add a reddish-brown tint to the hair. Though it’s natural, henna can cause irritation and reaction in the scalp, particularly if it is left on for too long or the woman in question has sensitive skin. Scalp irritation and resultant hair loss can also come about if henna is not thoroughly rinsed after application.
To ensure that all the henna is washed from the scalp after application, rinsing should continue until the water runs clear.