Any meds can be photosenstive and one needs to use sense and sunscreen, regardless if you are on meds or not.
The fatal rash that Lamictal can cause happens within 24-48 hours after starting it in most cases, the other kind of mild rashing is not fatal and does subside, I still do not suggest going out and sunbathing, especially without the use of sunscreen and be sure to have plenty of water to prevent dehydrating, that can be dangerous too while on almost any med.
I use a mild soap called Cetaphil/antibacterial, they make several different kinds, I prefer the bar soap, it seems to keep my skin from rashing up.
Some of my dryness and faintest rashing I owe to being pre-menopausal, I get acne and oiliness in one part of my face and dryness around my hairline and behind the ears, ugh, even happened before Lamictal.
Our skin changes with age changes, so sometimes we can think it is our meds. the best thing is to always report any changes to the prescribing physician.
I wish you luck with this.

DE

In giving advice seek to help, not please your friend
SOLON