Which vitamin deficiency can cause dermatitis?

Niacin deficiency, also known as pellagra, is well-documented to cause dermatitis, alongside other symptoms such as diarrhea and dementia. The dermatitis associated with niacin deficiency typically presents as a scaly, rough rash that commonly appears on sun-exposed areas of the skin. This condition reflects the role of niacin in maintaining healthy skin, among other bodily functions.

In contrast, while other vitamins have specific roles in skin health, the direct link between their deficiencies and dermatitis is not as prominent or well-established as it is with niacin. For instance, vitamin C is primarily associated with scurvy, which affects skin integrity but not specifically dermatitis. Vitamin B12 is critical for nerve function and the production of red blood cells and can lead to skin issues, but dermatitis specifically is not a direct consequence of its deficiency. Vitamin K plays a significant role in blood clotting and bone health, with limited effects on the skin that do not typically result in dermatitis. Therefore, niacin's distinctive connection to dermatitis through the condition of pellagra underscores why it is regarded as the correct answer in this context.