I have used this shampoo 5 times, which means I washed my hair 5 times in 8 days (twice each time). It seems to significantly reduce seborrheic dermatitis, especially flakes and scales (although it leaves my hair very wild and the smell is so-so, it doesn't smell nice, but it smells better than tar-based shampoos). However, I think I will know for sure after 1 month. I also use Castalia Dermopur Emulsion as a lotion.

In the past, I have tried everything, from coal tar shampoos (IONIL, Tarmed) to Fungoral, Helsinki Formula, Selsun 1% (the 2.5% was effective), Daohair S, Ducray Kelual DS, Bionatar with ichthyol, Biotrin DS, etc. None of them helped, although they reduced the scales, the flakes were still many and the itching was constant...

Now let's see if BIODERMA DS+ continues to perform well. I will come back with a new comment soon because dermatitis is a big hassle.

Additional comment 28/2/2022:
I recently tried DUCRAY Kelual DS again, unfortunately, it does nothing, intense itching and many flakes... I also used IONIL 4.25%, which is a coal tar shampoo, it dries the scalp and I still have itching. Does BIODERMA DS+ do the job? Relatively, it doesn't eliminate the problem, but it reduces the flakes more and the itching is less. I see that it is the most effective for my skin. However, I wash my hair with it for 3 consecutive days, and on the 4th day when I don't wash it, I use CASTALIA Dermopur Emulsion lotion, which is okay but doesn't work wonders. I also have CASTALIA Dermopur Shampoo Integral 200ml, to which I add lavender, tea tree, and rosemary essential oils to make it stronger, but I use it occasionally, it is not as effective.

I have been to several dermatologists, but no solution has been found. The only shampoo that completely cured my problem was SELSUN 2.5%, which has been discontinued and now only the 1% version is available, which does nothing.

New additional comment 4/6/2022:
It seems that the formulation of the shampoo has changed. While the previous BIODERMA DS+ was beige and smelled somewhat strange, the new formulation is white with a softer scent. Its performance is so-so, as I described above. It seems that after a certain point, the fungus becomes accustomed to the substance, so I start using CASTALIA Dermopur Shampoo Integral, to which I have added several drops of essential oils (lavender, rosemary, tea tree), and the itching is somewhat reduced. I alternate between the two shampoos. My dermatologist told me that there is no cure, only the problem is somewhat suppressed with various products.