What Could Be Causing Sudden Acne And Skin Irritation After Having Clear Skin, Especially After Returning From Holiday?

I have never had acne and hardly any pimples. I always had super clear skin, even when I was a teen/in puberty. I am 21 now. I have so much acne and red bumps and spots and irritation on my face, what is this from and what can I do? I gave tried everything but it stays the same or gets worse. It really got much worse after I went on holiday and came back.