Blonde chemist assistant

The owner of the chemist shop walks in to find a guy leaning heavily against a wall.

The owner asks the blonde sales girl: 'What's with the bloke over there by the wall?'

The blonde responds: 'Well, he came in here this morning to get something for his cough. I couldn't find the cough syrup, so I gave him an entire bottle of laxative'

The owner, wide-eyed and excited shouts: 'You idiot! You can't treat a cough with a bottle of laxatives!'

The blonde calmly responds: 'Of course you can!,

Spoiler:

Look at him, he's afraid to cough.'

.... and who said blondes were dumb