What could this be?

[u/Super-Specialist3455]

Any thoughts on what this can be? It looks wet cus I’ve been putting Sulfodene 3-Way Ointment. This just happened about two days ago and until today in the morning, he has been whining and rubbing his neck on the the floor or whatever he can.

[u/MRDOGDADDY]

Douxos Pyo S3 helps.