>>82087122 (OP)Find the underlying medical cause, often diabetes but can also be iron chelation issues, lots of autoimmune diseases etc
Unironically worth a shot to fix your microbiome by drinking tons of kefir and eating fermented stuff, *might* fix it if you're lucky.
Otherwise tons of anti-inflammatory compounds, injecting glutathione for example. Theres also experimental melanon production disruptors, ie search for tyronase inhibitors and then laser the existing melanocytes away or use microneedling