Get him to the Vet!!!
Zorro had feline acne about 2 yrs ago. It looks like black dirt specks. Well he started to lose hair there, THEN it became infected!!! Red, pus filled pimply lookin things! I could tell it was painful.
I took him to the Vet & she gave him antibiotics to kill the infection. She recommended using a warm washcloth with DILUTED hydro-peroxide. The diluted stuff won't burn as much and it'll clean your kitty off.
If feline acne is let go like this the pimples do rupture and bleed. The infection is horrible. Zorro's went from looking like lil black dots to being infected kinda quickly.
So I think a vet visit in in order for Shamrock.
Also, do you use plastic bowls? I have heard that cats who drink from plastic bowls are more apt to getting the acne. My cats have porcelain bowls so I tihnk Zorro got his zits from the stress of MOVING.
The acne forms cuz their chin is a hard area to clean, or from stress, or, plastic bowls. Anyhoo love your kittie's name
and please get him to the doc.