Which of the following is classified as a contagious skin condition?

Ringworm is classified as a contagious skin condition because it is caused by a fungal infection, specifically dermatophytes, which can be easily spread from person to person or through contact with contaminated surfaces or objects, such as towels, clothing, or bedding. Due to its infectious nature, individuals with ringworm can transmit the fungus to others, and it can also affect different areas of the body, including the scalp, feet, and nails.

In contrast, conditions like psoriasis, contact dermatitis, and acne are not contagious. Psoriasis is an autoimmune condition characterized by rapid skin cell growth, leading to thickened patches of skin. Contact dermatitis results from an allergic reaction or irritation caused by a substance that touches the skin, and while it can be triggered by allergens, it is not spread from person to person. Acne is primarily linked to clogged pores and hormonal changes and does not involve infectious agents that can be transmitted between individuals. Therefore, ringworm stands out as the only option that poses a risk of contagion.