1
general::
Phrase(s): louse someone or something up
Inf. to ruin something; to mess someone or something up. • You really loused me up! You got me in a real mess! • Who loused up my scheme?
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Spoil, ruin, bungle. For example, The bad weather loused up our plans, or Your change of mind really loused me up. This slangy expression originated in World War I, when infestation with lice was the common lot of soldiers in the trenches; its figurative use dates from the 1930s.
American Heritage Idioms