Mosquitoes carry a lot of nasty diseases, including West Nile Virus. The WNV is carried by birds, that are bitten by mosquitoes, who then transfer it to humans and other animals.
The trick to avoiding all these mosquito-borne diseases is not to have them bite you in the first place.
Many aromatic herbs such as mint, catnip, rosemary and marigold have mosquito-repellent oils in them. These herbs, if applied to the skin and clothing can then repel mosquitoes.
To do this, you will usually want to put the herbs in a “medium” that will take on the repellent oils and chemicals present in the herbs — so that it can be easily applied. Such a “medium” can be vinegar or olive oil, for example. You will want to soak or mash the herbs in such a medium.
This is the idea behind such preparations as “Four Thieves Vinegar” which is vinegar — infused with insect-repellent herbs.