Good one, @ThelmaLou! I’m gonna use it too. 
I’m no expert, but that doesn’t look like shingles to me.
It’s obviously the creature inside trying to escape the dying host…
Eww, why did I look at that? When will I learn not to click the link?
I looked, I did not find it appalling, but then I have had stuff that was harmless that looked worse. Eczema, dermatitis, cellulitis, or psoriasis come to mind as possibilities that are at least as likely as anything mentioned so far. Of those four, cellulitis is potentially the most serious in the short term, I think, because it spreads and is contagious. My husband once had cellulitis on almost exactly that area (although I don’t think it included an open sore). I’ve had both eczema and dermatitis there (as well as lots of other places). Certainly it could also be an allergic reaction to something topical.
The topic of Jeffrey Epstein? 
Maybe it’s from shaking a lot of hands.
I agree that it’s ugly, but not appalling, and consistent with many relatively minor conditions.
One of the comments is:
I’ve also been experiencing a distressing dermatological condition. Whenever I see an image of Trump or hear his voice, my SKIN CRAWLS.
Sounds like a skin condition was afflicted with a bad case of Trump.
Official “explanation” from Trump’s house doc, Barbabella: “President Trump is using a very common cream on the right side of his neck, which is a preventative skin treatment, prescribed by the White House doctor. The president is using this treatment for one week, and the redness is expected to last for a few weeks.”
Nice explanation there, doc. 
What seems like a possible “preventative” treatment is that Trump has actinic keratoses or early non-invasive squamous cell skin cancer, and the “common cream” is to treat it so it doesn’t progress further.* Or something else like eczema, but you’d think there’d be no need for a mystery about that.
A patient treated with fluorouracil cream for actinic keratoses.
Docs who treat Presidents have typically been somewhat reticent, but this guy is in a class of his own when it comes to non-disclosure disclosures.
*might possibly explain the Trumpian hand lesion(s)
He’s outright lying, it seems to me. He strongly implies that the cream caused the rash/eruption.
But who else but a willing prevaricator would accept the job as Donald’s doctor???
Well, you see, Donald was using Oil of Olay (a very common cream) to beautify his skin, and he had this unexpected reaction…
The doc might’ve been technically correct in that a skin cream like fluorouracil (or as it’s colloquially known, 5-FU) causes a rash as it’s working to kill precancerous cells. But that would be ignoring an underlying skin condition.
Update: other docs are skeptical of Barbabella’s story too.
Yeah, that makes sense. But Barbarella’s propaganda was ‘it’s just a common cream, and this common cream commonly creates a rash for a few weeks’ which was intended to fend off any speculations about cancer and such. Of course we see how well that worked.
Jonathan Reiner’s observation (from your link) is smart—the statement may well have been written by Trump’s caddy or someone else:
… or Putin and Bibi slapping the back of his neck …
The weeping sores set off the wattles nicely.
I’ve been reading Cornelius Ryan’s The Last Battle, about the final days of WWII and the Russian and American drives on Berlin.
By sheer coincidence, this evening I came across a passage about a major dental procedure that Hitler had in 1944, and how details were kept from everyone outside his immediate circle. “One of the cardinal rules for those who worked for the Fuhrer was that everything about him, especially his illnesses, remain top secret.”
The Circle of Life… (or is that ringworm?)
I think it may be time for a song.
Would everyone please refill their drink and step to the piano? Please.
…
♫ We’re Off to Impeach the Lizard…!
♫ The Fat Orange Lizard of Pus…!
♫ We hear he is a pants full of shit
♫ And smells like Gangreneos Pus…!
♫ If an Impeachable Leach he was
♫ He was he was. He was he was.
♫ He was he was.
♫ He was he was.
♫ He WAS…!
( ♫ Because of the Son Of A Bitch He Was ! )
< Orchestral Sound Effect >
♫ We’re Off to Impeach the Lizard…!
♫ The Fat Orange Lizard of Pus…!
♫ We’re off to kill the wizard
And set up our own fascist state! ♫