Yep, she has a skin condition. I didn’t know this, so I looked it up. I guess it’s not super common knowledge, but she has discussed it before.

One of the fans asked Terry Farrell about her skin disorder, which prevented her from doing much shooting outside, such as the episode Rocks and Shoals where Dax stays inside a cave for most of the episode. Farrell told how she was teased when people saw her about walking about with a parasol.