This depends on the type and severity of a skin condition. For instance, if a patient is suffering from red, irritated patches of skin, many dermatologists will simply examine the patient’s skin to determine if it’s psoriasis, eczema, or contact dermatitis, which are very common. In other situations, such as in the case of a patient having a suspicious mole, a skin biopsy might be required to determine if the mole is skin cancer or a benign (noncancerous) skin growth. How a dermatologist evaluates, diagnoses, and treats a skin condition wholly depends on the type of skin condition, its severity, and how it’s impacting the patient.