I have a darkish patch on my arm. i thought it was a ringworm and tooking deworming tablets and gave it a few days, nothing's changed?

Doctor can look: Words can fool you. A fortification is a large fort, but a ratification is not a large rat. Ringworm is not a worm problem, but is a rash cause by fungi. The medical term for the condition is tinea corporis. Anyway, there are also other conditions that can cause a darkish patch on one's skin, so one's primary care doctor should take a look. An online virtual consultation might work too.