If you're one of the people who gets frequent bug bites, there's always a time and place for insect repellent.
Sometimes you may even need to use them in your own home. You might also try using a fan, they are not strong fliers. And thick clothing, or multiple / baggy layers will protect you as well. Isolate the problem by closing your bedroom door (this could also save your life during a fire at night). In the morning, you'll want to search doors & windows and on walls, or where it sneaked in. You can grab them with a napkin or vacuum them, they are much slower than normal flies. You can also use electronic traps at night.
If you can't avoid a few bites, many store-bought itch remedies are ammonia-based. A dilute mix of 1 part store-bought ammonia and 20 parts water will serve just fine applied a few times daily or as needed.
DEET
Note
DEET damages synthetic clothing and many types of plastics & composites.
The original insect deterrent. Does not so much "repel" mosquitoes and ticks as it does confuse them and "disable" the biting behavior. They will still land, but if properly applied, not bite.
This one is completely synthetic, made in a lab. But nothing very bad can be said about it, other than applying it regularly to your face is probably not advised. There have not been many scientific studies showing harmful effects when used in moderation.
I do not use this as much as the others on this list. But if I need to seal off a window or enforce a perimeter, I will spray down equipment or relevant areas. I will use it on cotton clothing (e.g. thin T-shirts), and occasionally on exposed skin (legs, feet, arms, shoulders).
Lemon Eucalyptus Oil
This can be purchased in a relatively pure form online. I've transferred mine to amber glass with pump-action spray nozzles, because the plastic bottles it comes in do not spray as well.
It is safe with clothing & skin, and more "natural" than some of the others.
Effective against ticks & mosquitoes for 8-12 hours.
Picaridin
Effective, long-lasting (12+ hours), available as a pump spray, semi-natural, non-irritating (except to the eyes & mouth), affordable, safe on clothing & skin, and my personal favorite.
Slightly oily residue.
IR3535
Note
Must be used outside in a well-ventilated area; causes vigorous respiratory irritation.
As effective as the others, without lasting as long (~8 hours).
Safe on skin & clothing.
Only a few brands available; comes in an aerosol spray (must be used before it loses pressure).