It seems like the product isn't suitable for your skin. When I was looking for a Vitamin C serum locally available, I was keen on buying this serum as well since it's so cheap. But after reading a lot of reviews, I decided not to. Many reviewers had a similar experience to yours.
3. L’Oréal Revitalift Clinical 12% Pure Vitamin C Serum: Best vitamin C serum for healing environmental damage. Price: £30 (30ml) | Buy now from Boots If environmental damage from sun and air
I really like Garnier Vitamin C 2in1 Brightening Serum Cream. The texture is nice, smooth and leaves my skin bright and moisture. I have combination skin with oily T-zone and after around 2 weeks of using serum- cream that T-zone starts shining too much, but skin on cheeks are well moisturised. Overall Garnier Vitamin C serum cream leaves my 0zTETm.