If you have color-treated hair or a sensitive scalp, you can still use this shampoo-paste, but you need to be careful. The active ingredient, selenium disulfide, is a strong component, so your scalp may react differently than it would to a regular shampoo. The product itself notes that it should be introduced carefully and that you should watch how your skin responds.
Before using it on your whole scalp, do a small patch test. Apply a tiny amount to a small area behind your ear or on the back of your scalp, leave it on for the usual contact time, then rinse. Wait 24 hours to see if any redness, itching, or irritation appears. If you notice any reaction, do not use the product.
When you start using it, use a smaller amount than you would with a regular shampoo and only on the scalp, not on the hair lengths. If you have color-treated hair, note that strong anti-dandruff ingredients can sometimes affect hair color, so it is wise to use the product only on the scalp and rinse it out thoroughly to minimize contact with the colored hair.
Also, avoid using this product at the same time as other strong scalp treatments, such as other medicated shampoos, exfoliating scrubs, or leave-on scalp serums that contain active ingredients. Combining them can over-stress the scalp. If you are already using a strong treatment, either alternate days or stop the other product while you use this one, depending on what your scalp tolerates.