The ingredients will need to be stockpiled because they are not all readily made in a post-event world.
There are source links in the original article which I've edited in the quote, below.
http://thehomesteadinghippy.com/diy-natural-flea-repellent-for-dogs-why-you-need-this/Ingredients for natural flea repellent - 1/2 Cup of Food Grade Diatomaceous Earth
- 1/4 Cup Powdered Yarrow
- 1/4 Cup Neem Powder
- 10 Drops Cedar Essential Oil
Directions to make your natural flea repellent 1. Place all ingredients in a sealed jar and shake until well blended.
2. Keep in a sealed container until needed.
3. Shake powder in hand and apply liberally from the shoulder to the tail and from the chest to the groin.
The container I use is a pint mason jar with a parmesan cheese lid. This recipe should last you for several applications.