Bio has enzymes, non bio doesn’t.
There’s a wide misconception here in the UK that enzymes are bad for skin, so non bio is marketed as sensitive skin detergent.
In reality - it is just a load of clever marketing, especially as a lot of non bio is heavily scented. Ironically the only detergent I am allergic to here is a big brand non bio, yet the biological products from their sister brands are absolutely fine for me. In real terms, you are sacrificing cleaning performance for the misbelief that it is better for your skin. A lot of people will then buy stain removers such as Vanish etc to compensate for the poorer cleaning, not realising that with most stain removers they are adding back in the enzymes that they don’t want in the first place.
These “non bio” products are often sold alongside matching scent boosters and fragrance softeners, which are a big no if you do have sensitive skin. In most circumstances those with sensitive skin (such as myself) are better off using a bio detergent, using extra rinse if needed and using either no softener at all, or a fragrance free alternative. You often see people in the supermarkets here buying non bio detergent, and then putting heavily fragranced softeners and scent boosters in their trolley alongside, not realising that the detergent isn’t the problem in most cases.
The only practical non bio detergents are delicate ones for silk & wool, where enzymes can damage these fibres.
Hope this helps
Jon