Final answer:
Tinea capitis, a fungal infection, cannot be treated in a salon and requires medical intervention, unlike some other hair and scalp conditions.
Step-by-step explanation:
Among the hair and scalp disorders listed, Tinea capitis cannot be treated in a salon. Tinea capitis, also known as scalp ringworm, is a fungal infection that affects the scalp. As this is a medical condition, it requires antifungal medications prescribed by a healthcare professional. Therefore, it should not and cannot be treated in a salon setting, which is not equipped to provide medical treatments for fungal infections. In contrast, conditions such as dandruff, alopecia areata, and psoriasis can be managed with the use of specialty shampoos and treatments available at salons, although more severe cases may still require medical attention.