How should this serum be used — on the scalp or along the lengths?

This serum was created first and foremost as scalp care: urea and allantoin work exactly where the skin becomes dry, tight or sensitive. So most of the product should be applied evenly to the scalp — in small amounts, spreading it with your fingertips or with an applicator if the packaging includes one.

The serum can also be used on the lengths — especially if the hair is brittle, tangles easily and loses its smoothness. In this case, a small amount of the product is spread over damp or towel-dried hair, avoiding the roots so as not to weigh them down.

The most convenient time to use the serum is after washing your hair: at that point the scalp is clean and more receptive to moisturising ingredients. There is no need to rinse it off — the formula is designed as a leave-in. You can use a hairdryer after applying it, but at a high drying temperature keep the dryer at a distance from your scalp.

If your scalp is sensitive, it is sensible to start with a small amount when using a new product for the first time and to watch for any reaction over several days.