This saying is used to refer to the idea that when someone is having a hard time, all the problems seem to pile on. It can be translated literally as 'to the skinny dog, all fleas fall'.
Examples
- Spanish: Desde que perdió su trabajo, Juan no ha parado de tener problemas. Ya sabes, al perro flaco, todas las pulgas le caen.
- English: Since he lost his job, Juan has not stopped having problems. You know, when it rains, it pours.