Self harm and anger

Hi,

I'm new here and looking for some advice please. My 18 year old son is really struggling at the moment. He had a complete meltdown this morning due to the fact his towel had touched someone else's. He started screaming, crying and swearing which then led to him cutting his arm. I have told him he needs to see a gp but he refuses to go.

Has anyone got any advice on how to deal with these rages? They are scary for everyone in the house he's 6ft1. 

He gets up and goes to work every morning but for some reason mornings really trigger him.

Thank you for reading