The most common adverse effects of oral isotretinoin (>1/10) are: cheilitis, skin dryness, erythema, itching, scaling, bruising, skin atopy, conjunctivitis, dry eyes and eyelid inflammation. The aim of this work was to define an optimal dose regime of the oral isotretinoin allowing for effective reduction of sebum production and minimalization of adverse effects such as decreased skin ... [Show full abstract] moisturization, increase in TEWL and intensified erythema. The skin parameters were assessed using the MPA 5 diagnostic apparatus. Moisturization together with an increase in TEWL and erythema during treatment with isotretinoin seem to be crucial factors responsible for patient discomfort. The decrease in the pigment content in the skin during retinoid treatment is a favourable symptom, due to the frequent tendency of skin pigmentation disturbances in the sites after acne changes. On the basis of performed analyses it was concluded that the new therapy schema is the most advantageous form of isotretinoin dosing and it involves the use of a constant drug dose - 0.4-1.0 mg/kg body mass/day without modification during treatment.