I realise than there is a lot of things about medicine involves the number 7.
The "SEVEN" rules
1. Combined oral contraceptive pills : Take 7 active pills to get covered
2. Head lice treatment : Repeat after 7 days ( 1 week)
3. Scabies : Repeat after 7 days
4. Most antifungal products : Continue using for 1 or 2 weeks ( 7 to 14 days) after the symptoms have ceased.
5. Lamisil® AT Spray direction: once a day for 7 days
I think there are more, but I can't remember at this stage.