Because anti-salmonella the woman's immune system to recognize the pathogen (salmonella) and kills it.
Explanation:
Anti-salmonella is a serum containing inactive salmonella serotypes. They are effective in cases of salmonella infection where antibiotic use did not work and the patient's immune system was unable to recognize the pathogen and kill it. Anti-salmonella serum allows the patient's immune system to adapt, recognize the pathogen and get it expelled from the patient's body.
Males get very aroused around their partner they find sexually attractive and the male sex hormone known as testoterone is going crazy. If you want a more specific answer I'd reccomend researching the male anatomy.