I notice that sea bathing was particularly recommended for skin diseases and tuberculosis, according to the sub-title of Dr. Russel's book, and that the original was apparently written in Latin before being translated into English. I've linked a Wikipedia article on scrofula ("the king's evil") which it turns out could be either a skin disease *or* TB(!).

Julie, your post makes me realize that along with the pleasure-seekers who went to Brighton just to enjoy themselves, there must have been a fair number of people in the streets who clearly had something wrong with them, as you can see even today in European spa towns. Of course, I imagine it was fairly easy for Lydia to ignore or overlook them and see only what she wanted to see...