Hi and welcome
You have a gorgeous Swiss teddy there!
Unfortunately, it is impossible to tell what he has on his fur for sure without a hands-on examination but it looks like some rather large skin flakes.
Please be aware that one-off pet shop strength ivermectin doesn't work, nor will lice shampoo on spec (especially with no lice to be seen) - it's just a waste of money. Please have your boy vet checked for potential skin parasites or a fungal skin infection and the appropriate vet strength products. Any vet strength parasite treatment needs to be at least three rounds at the product specific interval to be effective.
Only once both mites (neither mange nor hay mites are visible) and a fungal skin infection have been excluded, can you diagnose 'teddy skin', which is a skin condition particular to teddy breeds (both American and Swiss teddies) due to their thick coat. It can affect some individuals quite badly while others will never suffer from it.
However, this is not a process you should do at home with low dosed one-off products as you can condemn your piggy to months of unnecessary suffering from undertreated skin parasites. In the end, it is much cheaper to pay for the vet and do it properly instead of spending money on inappropriate products and then needing to see a vet with an advanced case.
I have always made sure that I have seen a vet and done the full exploration with them with my own teddies suffering from this incurable breed sprecific complaint.
Here is more information on skin parasites and their proper treatment:
New Guinea Pig Problems: Sexing & Pregnancy; URI, Ringworm & Parasites; Vet Checks & Customer Rights