It is realistic to judge this shampoo after several weeks of regular use, not after the first wash. Dandruff is linked with several scalp factors at the same time: more active Malassezia yeast on the scalp surface, increased sebum, and dead skin cells clumping into visible flakes. A single wash can remove some oil and loose flakes, but it does not show how the scalp will respond to a consistent routine.
Use RADICAL Anti-Dandruff Shampoo two or three times weekly as directed and pay attention to practical signs: whether flakes return more slowly after washing, whether the scalp feels less itchy, and whether oily build-up is easier to manage. Taking a simple mental note of your baseline can help, because dandruff often fluctuates with season, stress, styling products and how often the hair is washed.
If the scalp feels very dry after use, adjust the routine rather than stopping immediately: apply the shampoo mainly to the roots, let the foam rinse through the lengths, and use conditioner on the lengths if needed. You can also alternate with a milder shampoo between anti-dandruff washes, as suggested in the product guidance.
If redness, irritation or persistent itching does not improve after several weeks of regular use, consult a dermatologist or trichologist, because similar symptoms can also occur with conditions such as seborrheic dermatitis, psoriasis or contact allergy.