Sunlight exposure is very important for things such as preventing seasonal effective disorder (SAD), vitamin D synthesis and immune stimulation. It does not do the same things as a sauna though unless you live is a really warm and sunny climate. You can sunbathe in the middle of Alaska on a sunny day when it is 32F (0C) and you will not be sweating out toxins. You won't look very tan either, you will look more like a Smurf!