Is it okay to use a face wash twice a day?
The trouble is that not all face-washes are made equal…
The short answer is, if the product was made by a reputable manufacturer, and it is called a face-wash, it ought to be safe to use twice a day. Although I would expect the packaging to advise at most, once a day (the advice we give on our products needs to be safe for everyone, so we tend to set limits based on someone with very sensitive skin using it in generous doses. So, if you’ve used it twice a day, and you’re asking will that do harm, don’t worry, your skin will be ok.
If you are asking - should you do this? I would need to know what the ingredients are, and there are many possible variations in a face-wash. But the majority are usually designed to be used a couple of times a week and using it more often could dry your skin or irritate it, especially the areas around eyes and lips.
As technically, a bar of soap is a face-wash, so is water, I am going to assume that you are describing a gel-like wash, designed to either exfoliate a little, or thoroughly remove make-up or dust/daily grime for people working outside or in heavy industry. If it’s the latter, I think once a day would be kinder to your skin. Unless it has a low pH (4–6) and lots of emollient ingredients on board, in which case, it would probably say, somewhere on the packaging that it is formulated specifically for dry and sensitive skin. On the whole, the best advice is usually to follow the directions given on the pack.
As for how long to leave it, I would imagine it is designed to be washed off as soon as it has lathered, if it doesn’t lather, as soon as the skin is covered and you’ve gently rubbed it in to the edges on your nose, chin, neck and forehead (avoid eyes and mouth areas).
My slight concern is why you might be wanting to use it twice a day. If it’s simply removing make-up/dust etc, no problem. But if you are trying to dry out oily skin, this isn’t the route I would recommend. Just remember to be gentle with your skin, it usually works best when just a few staples are applied, to help it do its job.