I love chemicals! We wouldn't be here without chemistry, gold wouldn't exist and the earth would just be a piece of rock floating in an empty universe.
You are a walking chemical factory!
Anyway, back to the question...
Mozzie, flea, fly and other bites are in itself nothing special. It's your body responding to an alien substance, like insect saliva, or bacteria on their bity parts, that causes the itch. Your body responds by causing a small inflammation around the bite and it's this inflammation that causes the itch. Some bodies (mine, and by the looks of it, yours as well) go a bit overboard in this reaction and send a whole area into overdrive, or sometimes there's just so many bites per square cm that the itching becomes overwhelming. Cooling down the area, just like you would do with other injuries, with ice helps a lot to prevent or at least limit the development of inflammation and thus the dreaded itching.
Another thing to consider is numbing the affected area for a while. there's 2 things at work here: the inflammation that will cause the itching and the nerves in your skin which transport this pain/itch information to your brain. If you can numb those nerves long enough for the inflammation to run it's course, you are well on your way to preventing the secondary injuries of scratched skin (which will become itchy as well when healing) and spreading around the initial culprit, the alien particles, all over the area, into possibly broken skin, causing another reaction, and so on.
Soov (over the counter at a pharmacy) works very well for this. It contains lidocane to numb the nerves around the bite and an anti-inflammatory to calm down the bite itself. SO it cleans up the inflammation quicker and whilst doing so, you don't feel a thing!
If you are a bit wary of lidocaine, and you have some broken skin with (secondary) inflammation, you can dissolve a paracetamol in a little bit of water and dab the inflamed areas. The paracetamol will make short work of the inflammation. You can drink the rest for a bit of pain relief.
I would stay well away from rubbing metho into your skin. 95% of metho is awesome stuff (ethanol alcohol, gets ya legless in no time!), unfortunately the other 5% is its lethal witch of a cousin Methyl alcohol, or methanol. Even this small amount can leave you blind, or worse when it has a chance to enter your bloodstream.
Now, to keep them buggers off...
There's not much that keeps mozzies at bay. They've been around for a fair while longer then us and have been the bane of our existence since we first became sentient. Mankind has been trying to find a cure all for this scourge since our existence, since it's estimated that about half the people that ever existed have died from (the effects of) mosquito bites. So it's pretty safe to assume that there is no 1 method to keep them at bay, because if there was, we wouldn't lose 3000 people per day on the effects of mozzie bites still.
The sand fleas can be mitigated by staying covered, i.e. wear socks or put something sticky on your skin, like vaseline, they have difficulty getting through that and if they do, they can only bite once and then they are stuck. This doesn't work for mozzies though.
There's some encouraging results from experimenting with geranium soaked mozzie nets in Africa. The mozzies seem to not like geranium, or perhaps the geranium smell masks the co2 we expel well enough to make it difficult for them to home in on us as targets. The jury is still out the reason, but the results are good. If you can stand the smell, start growing geraniums and wash all your gear in geranium water.
Other than that there's various mozzie/flea/fly sprays with or without DEET. If you're traveling in area's where there are known mozzie borne diseases, be smart and use the 80% DEET sprays and nets and keep as much skin covered as possible. Everywhere else, it's up to you how much discomfort you can bear.
My personal kit contains the repellent spray (blue can) from the Aldi, which so far seems to work at least as well as the DEET laden Bushmans but is a lot less sticky, a strip of paracetamol, 1 or 2 tubes of Soov (or if I can't find Soov, lidocaine jelly that's used for tooth aches), a tube of betadine ointment to treat infected bites and insect wipes found at Woolies to wipe the dog when we find ourselves in fly infested pasture.
